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Most chemical agents (alcohols keftab 250 mg discount bacteria killing light, phenols order keftab 750mg with mastercard 5 infection control procedures, alde- hydes order keftab 125 mg with mastercard taking antibiotics for acne, heavy metals buy 375mg keftab otc antibiotic chicken, oxidants) denature proteins irreversibly. Physical Methods of Sterilization and Disinfection Heat The application of heat is a simple, cheap and effective method of killing pathogens. This is the antimicrobial treatment used for foods in li- quid form (milk): — Low-temperature pasteurization: 61. The guideline values for hot-air sterilizers are as follows: 180 8C for 30 minutes,160 8C for 120 minutes, whereby the objects to be sterilized must themselves reach these temperatures for the entire pre- scribed period. Autoclaves charged with saturated, pressurized steam are used for this purpose: — 121 8C, 15 minutes, one atmosphere of pressure (total: 202 kPa). In practical operation, the heating and equalibriating heatup and equalizing times must be added to these, i. When sterilizing liquids, a cooling time is also required to avoid boiling point retardation. In addition, the proteins of microorgan- isms are much more readily denatured in a moist environment than under dry conditions. Two types are used: — Gamma radiation consists of electromagnetic waves produced by nuclear disintegration (e. On a large scale, such systems are used only to sterilize bandages, suture material, plastic medical items, and heat-sensitive pharmaceuticals. The required dose depends on the level of product contamination (bioburden) and on how sensitive the contaminating microbes are to the radiation. Most of the available filters catch only bacteria and fungi, but with ultrafine filters viruses and even large molecules can be filtered out as well. These materials can be processed to produce thin filter layers with gauged and calibrated pore sizes. In conventional depth filters, liquids are put through a layer of fibrous material (e. The effectiveness of this type of filter is due largely to the principle of adsorption. Principles of Sterilization and Disinfection 39 Chemical Methods of Sterilization and Disinfection 1 Ethylene oxide. This highly reactive gas (C2H4O) is flammable, toxic, and a strong mucosal irritant. The gas has a high penetration capacity and can even get through some plastic foils. One drawback is that this gas cannot kill dried microorganisms and requires a relative humidity level of 40– 90% in the sterilizing chamber. Ethylene oxide goes into solution in plastics, rubber, and similar materials, therefore sterilized items must be allowed to stand for a longer period to ensure complete desorption. Formaldehyde irritates mucosa; skin contact may result in inflammations or allergic eczemas. In the past, it was commonly used in gaseous form to disinfect the air inside rooms (5 g/m3). The types of alcohol used in disinfection are ethanol (80%), propanol (60%), and isopropanol (70%). Due to their rapid action and good skin penetration, the main areas of application of al- cohols are surgical and hygienic disinfection of the skin and hands. Today, phenol derivatives substituted with organic groups and/or halo- gens (alkylated, arylated, and halogenated phenols), are widely used. One common feature of phenolic substances is their weak performance against spores and viruses. They bind to organic materials to a moderate degree only, making them suitable for disinfection of excreted materials. Chlorine, iodine, and derivatives of these halogens are suitable for use as disinfectants. Chlorine and iodine show a generalized microbicidal ef- fect and also kill spores. Calcium hypochlorite (chlorinated lime) can be used in nonspecific disinfec- tion of excretions. Chloramines are organic chlorine compounds that split off chlorine in aqueous solutions. The most important iodine preparations arethe solutions of iodine and potassium iodide in alcohol (tinc- ture of iodine) used to disinfect skin and small wounds. While iodo- phores are less irritant to the skin than pure iodine, they are also less effective as germicides. This group includes ozone, hydrogenperoxide, potassium perman- ganate, and peracetic acid. These substances (also known as surface-active agents, tensides, or detergents) include anionic, cationic, amphoteric, and nonionic detergent compounds, of which the cationic and amphoteric types are the most effec- tive (Fig. They have no effect at all on tuberculosis bacteria (with the exception of amphotensides), spores, or nonencapsulated viruses. Their efficacy is good against Gram-pos- itive bacteria, but less so against Gram-negative rods. Their advantages in- clude low toxicity levels, lack of odor, good skin tolerance, and a cleaning ef- fect. Practical Disinfection The objective of surgical hand disinfection is to render a surgeon’s hands as free of organisms as possible. Alcoholic preparations are best suited for this purpose, although they are not sporicidal and have only a brief duration of action. Principles of Sterilization and Disinfection 41 Alcohols are therefore often combined with other disinfectants (e. Alcohols and/or iodine compounds are suitable for disinfecting patient’s skin in preparation for surgery and injections. Strong-smelling agents are the logical choice for disinfection of ex- cretions (feces, sputum, urine, etc. Con- taminated hospital sewage can also be thermally disinfected (80–100 8C) if necessary. Suitable agents include aldehyde and phenol derivatives combined with surfactants. Instrument disinfection is used only for instruments that do not cause inju- ries to skin or mucosa (e. Laundry disinfection can be done by chemical means or in combination with heat treatment. The substances used include derivatives of phenols, alde- hydes and chlorine as well as surfactant compounds. Chlorine is the agent of choice for disinfection of drinking water and swimming-pool water. Final room disinfection is the procedure carried out after hospital care of an infection patient is completed and is applied to a room and all of its furnish- ings. Evaporation or atomization of formaldehyde (5 g/m3), which used to be the preferred method, requires an exposure period of six hours. This proce- dure is now being superseded by methods involving surface and spray dis- infection with products containing formaldehyde.
We cover the details of the nervous system in Chapter 15 buy keftab 500mg amex antibiotic 875, but here you can find out what’s happening as an impulse stimulates a skeletal muscle purchase keftab 375 mg without a prescription bacteria mod 1710. The impulse generic keftab 125mg visa 51 antimicrobial effectiveness testing, or stimulus order keftab 750mg antibiotic natural alternatives, from the central nervous system is brought to the muscle through a nerve called the motor, or efferent, nerve. On entering the muscle, the motor nerve fibers separate to distribute themselves among the thousands of muscle fibers. Because the muscle has more fibers than the motor nerve, individual nerve fibers branch repeatedly so that a single nerve fiber innervates from 5 to as many as 200 muscle fibers. These small terminal branches penetrate the sarcolemma and form a special structure known as the motor end plate, or synapse. This neuromuscular unit consisting of one motor neuron and all the muscle fibers that it innervates is called the motor unit. Interference — either chemical or physical — with the nerve pathway can affect the action of the muscle or stop the action altogether, resulting in muscle paralysis. There also are afferent, or sensory, nerves that carry information about muscle condition to the brain. When an impulse moves through the synapse and the motor unit, it must arrive virtu- ally simultaneously at each of the individual sarcomeres to create an efficient contrac- tion. The fiber’s membrane forms deep invaginations, or inward-folding sheaths, at the Z-line of the myofibrils. The resulting inward-reaching tubules ensure that the sarcomeres are stimulated at nearly the same time. In other words, if a single muscle fiber is going to contract, it’s going to do so to its fullest extent. Following are some practice questions that deal with muscle anatomy and contraction: 13. False Pulling Together: Muscles as Organs A muscle organ has two parts: The belly, composed predominantly of muscle fibers The tendon, composed of fibrous, or collagenous, regular connective tissue. If the tendon is a flat, sheet-like structure attaching a wide muscle, it’s called an aponeurosis. Each muscle fiber outside of the sarcolemma is surrounded by areolar connective tissue called endomysium that binds the fibers together into bundles called fasciculi (see Figure 6-2). Each bundle, or fasciculus, is surrounded by areolar connective tissue called perimysium. All the fasciculi together make up the belly of the muscle, which is surrounded by areolar connective tissue called the epimysium. Blood vessels, lymph vessels, and nerves pass into the fasciculus through areolar connective tissue called the trabecula. These blood vessels in turn branch off into capillaries that surround the muscle fibers in the endomysium. Fasciculus Epimysium Muscle fiber (cell) (wrapped by perimysium) (deep fascia) Tendon Figure 6-2: Connective tissue in a Perimysium Bone muscle. Endomysium Blood vessel (between fibers) Illustration by Imagineering Media Services Inc. Nonetheless, it has been demonstrated that fewer action potentials — a weaker stimulus, as it were — causes fewer motor units to become involved in a contraction. So it’s true that a muscle organ can have varying degrees of contrac- tion depending on the level of stimulation. As for how this can be so, one theory pro- poses that individual fibers have specific thresholds of excitation; thus, those with higher thresholds only respond to stronger stimuli. The other theory holds that the deeper a fiber is buried in the muscle, the less accessible it is to incoming stimuli. Complete fatigue occurs when no more twitches can be elicited, even with increasing intensity of stimulation. The short lapse of time between the application of a stimulus and the beginning of muscular response is called the latent period. Two types of muscle contraction relate to tone: Isometric: Occurs when a contracting muscle is unable to move a load (or heft a piece of luggage or push a building to one side). Isotonic: Occurs when the resistance offered by the load (or the gardening hoe or the cold can of soda) is less than the tension developed, thus shortening the muscle and resulting in mechanical work. Each muscle depends upon compan- ions in a muscle group to assist in executing a particular movement. Prime movers: Just as it sounds, these muscles are the workhorses that produce movement. Fixators or fixation muscles: These muscles serve to steady a part while other muscles execute movement. Synergists: These muscles control movement of the proximal joints so that the prime movers can bring about movements of distal joints. Which of the following statements finishes this sentence and makes it not true: A contracting muscle unable to move a load a. Isotonic motion Leveraging Muscular Power Skeletal muscle power is nothing without lever action. The bone acts as a rigid bar, the joint is the fulcrum, and the muscle applies the force. Levers are divided into the weight arm, the area between the fulcrum and the weight; and the power arm, the area between the fulcrum and the force. When the power arm is longer than the weight arm, less force is required to lift the weight, but range, or distance, and speed are sac- rificed. When the weight arm is longer, the range of action and speed increase, but power is sacrificed. Therefore, 90 degrees is the optimum angle for a muscle to attach to a bone and apply the greatest force. Three classes of levers are at work in the body: Class I, or seesaw: The fulcrum is located between the weight and the force being applied. An example is a nod of the head: The head-neck joint is the ful- crum, the head is the weight, and the muscles in the back of the neck apply the force. An example is standing on your tiptoes: The fulcrum is the joint between the toes and the foot, the weight is the body, and the muscles in the back of the leg at the heel bone apply the force. An example is flexing your arm and showing off your biceps: The elbow joint is the fulcrum, the weight is the lower arm and hand, and the biceps insertion on the lower arm applies the force. Here are the possible directions: Longitudinal: Fibers run parallel to each other, or longitudinally, the length of the muscle. Pennate: Fibers attach to the sides of the tendon, which extends the length of the muscle. These come in subcategories: • Unipennate, where fibers attach to one side of the tendon; example: tibialis posterior • Bipennate, where fibers attach to two sides of the tendon; example: rectus femoris • Multipennate, where fibers attach to many sides of the tendon; example: deltoideus Radiate: Fibers converge from a broad area into a common point.
You are a visiting nurse for a patient recover- ing from a stroke who is being taken care of by her daughter-in-law buy 500mg keftab mastercard shot of antibiotics for sinus infection, who is also the mother of 2-year-old twins keftab 375 mg mastercard antibiotic resistance and livestock. Severe anxiety: you notice that your patient’s daughter is restless and unfocused keftab 750 mg line antimicrobial herbs. Give an example of a situation in which you experienced the following coping mechanisms personally or witnessed them in a friend effective 125mg keftab infection 6 weeks after hysterectomy, rela- tive, or patient. List three examples of situations in which stress may have a positive impact on an 11. Study Guide for Fundamentals of Nursing: The Art and Science of Nursing Care, 7th Edition. Scenario: Joan Rogerrio is a middle-aged woman with a history of inﬂammatory bowel c. What would be a successful outcome for this if he can make his mortgage and school patient? He put pressure on himself to be “the best” in sports and schoolwork and says he couldn’t handle the stress without getting high. What intellectual, technical, interpersonal, and/or ethical/legal competencies are most How would you use your knowledge of the likely to bring about the desired outcome? Think of a period in your life when you were under a considerable amount of stress, such as during exams, following a death, or during an illness. What resources might be helpful for to compensate for the effects of stress on your Ms. Study Guide for Fundamentals of Nursing: The Art and Science of Nursing Care, 7th Edition. Read the following patient care study and use your nursing process skills to answer the questions below. Scenario: Tisha Brent, age 52, comes to the clinic complaining of feelings of nervousness and an inability to sleep. Brent works full time as a social worker but is ﬁnding it more and more difﬁcult to help others because of her own worries. What are the steps of crisis intervention that because she must care for her husband. Findings from the physical assessment included a weight loss of 10 pounds in the past 3 months (with weight 5% below normal for height), tachycardia, slightly elevated blood 7. Study Guide for Fundamentals of Nursing: The Art and Science of Nursing Care, 7th Edition. Which of the following stages of grief, accord- will help establish a trusting nurse–patient ing to Engel, involve the rituals surrounding relationship? The nurse should encourage family express his feelings of loss and at times denies members to assist in his nursing care. The nurse should arrange a visit from a of grief would the husband be experiencing? A nurse informs a woman that there is nothing more that can be done medically for c. The coroner must be notiﬁed to determine followed by acceptance of the loss, is which of the need for an autopsy. Explain the entire condition in detail complained of frequent headaches and loss of regardless of what the patient may already appetite. Which of the following diagnoses speciﬁcally the patient from your goal of dispensing addresses human response to loss and impend- information. In a living will, a patient appoints an agent Circle the letters that correspond to the best that he/she trusts to make decisions if answers for each question. Which of the following are impending signs of healthcare team to resuscitate a terminal death? Increased gastrointestinal activity describe the process of preparing a death certiﬁcate? Lowered blood pressure health department, which compiles many statistics from the information. Study Guide for Fundamentals of Nursing: The Art and Science of Nursing Care, 7th Edition. It is the nurse’s responsibility to ensure Match the term in Part A with the appropriate that the physician has signed a death deﬁnition listed in Part B. A death certiﬁcate is signed by the patholo- gist, the coroner, and others in special a. The period of acceptance of loss during dentures or other prostheses which the person learns to deal with the e. Arranging for family members to view loss the body before it is discharged to the 2. A type of loss in which a person displays mortician loss and grief behaviors for a loss that has f. Attending the funeral of a deceased yet to take place patient and making follow-up visits to 3. A type of loss that can be recognized by the family others as well as by the person sustaining the loss 4. When an older man grieves for the loss of his youth, this type of loss is known as 6. Match Engel’s six stages of grief listed in Part A with the appropriate conversation that may 4. Abnormal or distorted grief that may be unre- occur during each stage listed in Part B. Resolving the loss Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins. Study Guide for Fundamentals of Nursing: The Art and Science of Nursing Care, 7th Edition. A slow-code order may be written on the chart Maybe my husband and I can eat out of a terminally ill patient if the patient or this Sunday. Terminal weaning is the gradual withdrawal of wish I could be more like her with my mechanical ventilation from a patient with a kids. The nurse assumes responsibility for handling to pray for my mother’s soul and to help and ﬁling the death certiﬁcate with proper me get over her death. A person experiencing abbreviated grief may have trouble expressing feelings of loss or may a. In the denial and isolation stage of dying, the patient expresses rage and hostility and adopts a “why me? Brieﬂy describe the following stages of dying, is usually responsible for deciding what and according to Kübler-Ross.
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It has also been suggested that improved psychological state is related to the social activity often associated with exercise and the resulting increased conﬁdence and self-esteem purchase 125mg keftab fast delivery bacteria background. Any reduction in levels of depression may be related to greater social contact discount 500 mg keftab amex antibiotics for acne during pregnancy, improved social support and increased self- eﬃcacy buy discount keftab 500mg antibiotics for acne what to expect. Because of the experimental design cheap 500mg keftab with visa infection jobs, the results allow some conclusions to be made about the direction of causality. However, as with many health- related behaviours, adherence to health promotion recommendations may be more motivated by short-term immediate eﬀects (e. Therefore, understanding the immediate eﬀects of exercise on mood has obvious implications for encouraging individuals to take regular exercise. Methodology Subjects The subjects were 36 male amateur athletes who were regularly involved in a variety of sports and exercised for more than 30 minutes at least three times per week, and 36 inactive men who exercised for less than 30 minutes per week. Design All subjects took part in two exercise sessions and completed measures of mood before and after each exercise session. Procedure At session one, all subjects completed a set of proﬁle questionnaires (back- ground physical and psychological measures) and took part in a maximal exercise session on a cycle ergonometer. At session two, subjects were randomly allocated to 20 minutes of either maximal, moderate or minimal exercise. All subjects completed ratings of mood before exercise, 2 minutes after exercise and after 30 minutes of recovery. Measures The subjects rated items relating to tension/anxiety, mental vigour, depression/dejection, exhilaration and perceived exertion before and after each exercise session. In addition, all subjects completed measures of (1) personality and (2) trait anxiety once only at the beginning of the ﬁrst session. Results The results were analysed to examine the eﬀect of the diﬀering degrees of exercise on changes in mood in the sportsmen and the inactive men. However, all subjects reported increased exhilaration and increased mental vigour two minutes after both the maximal and moderate exercise compared with the minimal condition, and in addition, the increase in exhilaration was maintained after the 30 minutes of recovery. Conclusion The authors conclude that both maximal and moderate exercise results in beneﬁcial changes in both mental vigour and exhilaration in both sportsmen and inactive men and suggest that ‘exercise leads to positive mood changes even among people who are unaccustomed to physical exertion’. They also suggest that greater attention to the immediate eﬀects of exercise may improve adherence to exercise programmes. Because of the potential beneﬁts of exercise, research has evaluated which factors are related to exercise behaviour. The determinants of exercise can be categorized as either social/political or individual. Social/political predictors of exercise An increased reliance on technology and reduced daily activity in paid and domestic work may have resulted in an increase in the number of people having relatively seden- tary lifestyles. In addition, a shift towards a belief that exercise is good for an individual’s well-being and is relevant for everyone has set the scene for social and political changes in terms of emphasizing exercise. Therefore, since the late 1960s many government initiatives have aimed to promote sport and exercise. Factors such as the availability of facilities and cultural attitudes towards exercise may be related to individual participa- tion. Consequently, the Sports Council launched an oﬃcial campaign in 1972 in an attempt to create a suitable climate for increasing exercise behaviour. Initiatives such as ‘Sport for All’, ‘Fun Runs’ and targets for council facilities, such as swimming pools and sports centres, were part of this initiative. In collaboration with the Sports Council, McIntosh and Charlton (1985) reported that the provision of council services had exceeded the Sports Council’s targets by 100 per cent. This evaluation concluded that: s Central government funding for sport and speciﬁc local authority allocations have helped participation in sport. This could take the form of vouchers for free access to the local leisure centre, an exercise routine with a health and ﬁtness advisor at the leisure centre, or recommendations from the health and ﬁtness advisor to follow a home-based exercise programme, such as walking. An alternative and more simple approach involves the promotion of stair rather than escalator or lift use. In addition, they can target the most sedentary members of the population who are least likely to adopt more structured forms of exercise. This is in line with calls to promote changes in exercise behaviour which can be incorporated into everyday life (Dunn et al. Research also indicates that stair climbing can lead to weight loss, improved ﬁtness and energy expenditure and reduced risk of osteoporosis in women (e. For example, some research has explored the impact of motivational posters between stairs and escalators or lifts and has shown that such a simple intervention can increase stair walking (e. The results showed that larger posters were more eﬀective at promoting stair use, that eﬀectiveness was not related overall to whether the message emphasized time and health (i. Therefore, these initiatives have aimed to develop a suitable climate for promoting exercise. In addition, as a result of government emphasis on exercise, speciﬁc exercise programmes have been established in an attempt to assess the best means of encouraging participation. In particular it is possible to diﬀerentiate between individual and supervised exercise programmes. Using random telephone numbers they identiﬁed 357 adults, aged 50–65, who led relatively sedentary lifestyles. These subjects were then randomly allocated to one of four groups: s Group 1: the subjects were encouraged to attend a one-hour vigorous exercise session at a local community centre at least three times a week. The results showed greater adherence in the unsupervised home-based programmes, than in the supervised programme. However, all subjects who had been instructed to do some exercise showed an increase in cardiovascular ﬁtness compared with the control group. The authors suggested that the results from this study provide insights into the development of successful national campaigns to promote exercise behaviour that involve a minimal and cheap intervention and argued for an emphasis on unsupervised individual exercising. Other factors that appear to play a role in developing successful exercise programmes are the use of behavioural contracts, whereby the individual signs a contract with an instructor agreeing to participate in a programme for a set period of time (e. Oldridge and Jones 1983) and the use of instructor praise and feedback and ﬂexible goal-setting by the subject (e. These factors involve supervised exercise and suggest that individualized exercise programmes may not be the only form of intervention. The social/political climate therefore has implications for predicting and promoting exercise. However, even if councils provide the facilities and government programmes are established, individuals have to make decisions about whether or not to par- ticipate. Research has, therefore, also examined the individual predictors of exercise behaviour. Individual predictors of exercise Dishman and colleagues (Dishman 1982; Dishman and Gettman 1980) carried out a series of studies to examine the best individual predictors of exercise and suggested that these factors can be deﬁned as either non-modiﬁable or modiﬁable. Non-modiﬁable predictors of exercise Dishman (1982) reported that non-modiﬁable factors such as age, education, smoking, ease of access to facilities, body fat/weight and self-motivation were good predictors of exercise. The results of a prospective study indicated that the best predictors of exercise behaviour were low body fat, low weight and high self-motivation (Dishman and Gettman 1980). However, whether factors such as access to facilities and self-motivation should be regarded as non-modiﬁable is problematic.
One alternate possibility is that the causal direction is exactly opposite from what has been hypothesized discount keftab 750mg with amex antibiotics jaw pain. Perhaps children who have behaved aggressively at school develop residual excitement that leads them to want to watch violent television shows at home: Figure 2 safe keftab 750mg treatment for sinus infection home remedies. It is also possible that both causal directions are operating and that the two variables cause each other: Attributed to Charles Stangor Saylor purchase 250mg keftab visa antibiotic chicken. A common- causal variable is a variable that is not part of the research hypothesis but that causes both the predictor and the outcome variable and thus produces the observed correlation between them order keftab 375 mg visa antibiotics for acne treatment. In our example a potential common-causal variable is the discipline style of the children’s parents. Parents who use a harsh and punitive discipline style may produce children who both like to watch violent television and who behave aggressively in comparison to children whose parents use less harsh discipline: Figure 2. When the predictor and outcome variables are both caused by a common-causal variable, the observed relationship between them is said to be spurious. A spurious relationship is a relationship between two variables in which a common-causal variable produces and “explains away‖ the relationship. If effects of the common-causal variable were taken away, or controlled for, the relationship between the predictor and outcome variables would disappear. In the example the relationship between aggression and television viewing might be spurious because by controlling for the effect of the parents’ disciplining style, the relationship between television viewing and aggressive behavior might go away. Common-causal variables in correlational research designs can be thought of as “mystery‖ variables because, as they have not been measured, their presence and identity are usually unknown to the researcher. Since it is not possible to measure every variable that could cause both the predictor and outcome variables, the existence of an unknown common-causal variable is always a possibility. For this reason, we are left with the basic limitation of correlational Attributed to Charles Stangor Saylor. It is important that when you read about correlational research projects, you keep in mind the possibility of spurious relationships, and be sure to interpret the findings appropriately. Although correlational research is sometimes reported as demonstrating causality without any mention being made of the possibility of reverse causation or common-causal variables, informed consumers of research, like you, are aware of these interpretational problems. One strength is that they can be used when experimental research is not possible because the predictor variables cannot be manipulated. Correlational designs also have the advantage of allowing the researcher to study behavior as it occurs in everyday life. And we can also use correlational designs to make predictions—for instance, to predict from the scores on their battery of tests the success of job trainees during a training session. But we cannot use such correlational information to determine whether the training caused better job performance. Experimental Research: Understanding the Causes of Behavior The goal of experimental research design is to provide more definitive conclusions about the causal relationships among the variables in the research hypothesis than is available from correlational designs. In an experimental research design, the variables of interest are called the independent variable(or variables) and the dependent variable. The independent variable in an experiment is the causing variable that is created (manipulated) by the experimenter. The dependent variable in an experiment is a measured variable that is expected to be influenced by the experimental manipulation. The research hypothesis suggests that the manipulated independent variable or variables will cause changes in the measured dependent variables. We can diagram the research hypothesis by using an arrow that points in one direction. The study was designed to test the hypothesis that viewing violent video games would increase aggressive behavior. In this research, male and female undergraduates from Iowa State University were given a chance to play with either a violent video game (Wolfenstein 3D) or a nonviolent video game (Myst). During the experimental session, the participants played their assigned video games for 15 minutes. Then, after the play, each participant played a competitive game with an opponent in which the participant could deliver blasts of white noise through the earphones of the opponent. The operational definition of the dependent variable (aggressive behavior) was the level and duration of noise delivered to the opponent. For one, they guarantee that the independent variable occurs prior to the measurement of the dependent variable. Second, the influence of common-causal variables is controlled, and thus eliminated, by creating initial equivalence among the participants in each of the experimental conditions before the manipulation occurs. The most common method of creating equivalence among the experimental conditions is through random assignment to conditions, a procedure in which the condition that each participant is assigned to is determined through a random process, such as drawing numbers out of an envelope or using a random number table. Anderson and Dill first randomly assigned about 100 participants to each of their two groups (Group A and Group B). Because they used random assignment to conditions, they could be confident that, before the experimental manipulation occurred, the students in Group A were, on average, equivalent to the students in Group B on every possible variable, including variables that are likely to be related to aggression, such as parental discipline style, peer relationships, hormone levels, diet—and in fact everything else. Then, after they had created initial equivalence, Anderson and Dill created the experimental manipulation—they had the participants in Group A play the violent game and the participants in Group B play the nonviolent game. Then they compared the dependent variable (the white noise blasts) between the two groups, finding that the students who had viewed the violent video game gave significantly longer noise blasts than did the students who had played the nonviolent game. Anderson and Dill had from the outset created initial equivalence between the groups. This initial equivalence allowed them to observe differences in the white noise levels between the two groups after the experimental manipulation, leading to the conclusion that it was the independent variable (and not some other variable) that caused these differences. The idea is that the only thing that was different between the students in the two groups was the video game they had played. One is that they are often conducted in laboratory situations rather than in the everyday lives of people. Therefore, we do not know whether results that we find in a laboratory setting will necessarily hold up in everyday life. Second, and more important, is that some of the most interesting and key social variables cannot be experimentally manipulated. If we want to study the influence of the size of a mob on the destructiveness of its behavior, or to compare the personality characteristics of people who join suicide cults with those of people who do not join such cults, these relationships must be assessed using correlational designs, because it is simply not possible to experimentally manipulate these variables. The goal of these designs is to get a picture of the current thoughts, feelings, or behaviors in a given group of people. The variables may be presented on a scatter plot to visually show the relationships. The Pearson Correlation Coefficient (r) is a measure of the strength of linear relationship between two variables. The possibility of common-causal variables makes it impossible to draw causal conclusions from correlational research designs.