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Chapter 9

PSYB01 - Chapter 9 notes.doc

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Department
Psychology
Course
PSYB01H3
Professor
Anna Nagy
Semester
Summer

Description
Chapter 9 Conducting Experiments Selecting Research Participants The methods used to select participants has implications for generalizing the research results Recall most experiments involve sampling participants from the population of interest, which is composed of all individuals of interest to the researcher Samples may be drawn using probability sampling or non-probability sampling, but when it is important to accurately describe the entire population you must use probability sampling. Much research, however, is interested in testing hypothesis about behaviour, so the focus is the relationships between the variable being studied and testing predictions made based on theories of behaviour. In such cases, participants may be found in the easiest way possible non-probability sampling. Nothing is wrong with this as long as you recognize that this affects your ability to generalize your results to larger populations, though it is still possible to You also need to determine your sample size. Increasing the sample size increases the likelihood that results will be statistically significant because larger populations are better estimates of the true population values Manipulating the Independent Variable To manipulate the independent variable you must construct an operational definition of the variable you must turn a conceptual variable into a set of operations Also, the independent and dependent variables must be introduced within the context of the total experimental setting which is known as setting the stage Setting the Stage In setting the stage you must do two things: 1. provide the participants with the informed consent information needed for your study 2. explain to participants why the experiment is being conducted sometimes the rationale given is entirely truthful, but the researcher will rarely give the hypothesis because if participants know exactly what you are studying they may try to confirm the hypothesis. Therefore, you may tell the participants you are studying memory when you are actually studying a certain aspect of memory. If deception is initially necessary, you have an obligation to address the deception when you debrief the participants afterwards There are no clear cut rules for setting the stage except the experimental setting must seem plausible to the participants Types of Manipulation Straightforward Manipulation Researchers are usually able to manipulate a variable relatively simply by presenting written, verbal, or visual material to the participants Straightforward manipulation manipulated variables with instructions and stimulus presentations Stimuli may be presented verbally, in written form, via video tape, or over the computer Eg. A study on the impact of heath promotion brochures presented two types of brochures to women one with text only, and one with pictures Most memory research relies on straightforward manipulations. Eg Langdon displayed lists of words to participants and measured their recall. The word lists differed in phonological similarity: some words sounded alike like cat and hat and some did not. They found that lists with dissimilar words were recalled more accurately. Good examples of straightforward manipulation on page 168 Most manipulations of independent variables are done straightforward researchers vary the difficulty of material to be learned, motivation, the way questions are asked, etc, in a straightforward manner Staged Manipulations Less straightforward sometimes it is necessary to stage events during the experiment to manipulate the independent variable successfully. Aka staged or even manipulated Most frequently used for two reasons 1. to create some psychological state in the participants, such as frustration or anger 2. may be necessary to simulate some situation that occurs in real life, such as studying cognitive performance under conditions of multiple task demand staged manipulations frequently employ a confederate or an accomplice. Usually the confederate appears to be another participant. They are useful in creating a particular social situation. Eg in a study on aggression, the confederate and the participant are both told to wait in a room, where the confederate insults the participant in the anger condition but does not insult the participant in the no-anger condition. The classic experiment by Asch on conformity is an example of the use of confederates. When participants were told to match a line to the line of the same length, the multiple confederates unanimously gave the wrong answer. Because of this, the participants conformed and gave the same, clearly wrong answer as the confederates. Look at table 9.1 on page 170 Staged manipulations require a great deal of ingenuity and some acting ability on the part of the confederate, for they are meant to involve the participants in an ongoing social situation which they perceive to be real, not part of the experiment. Researchers assume that the result will be natural behaviour on the part of the participants However, such experiments may be difficult to replicate because they involve a great deal of interpersonal communication that is difficult to put into words A complex manipulation is also difficult to interpret because if there were many things happening during the experiment, what one thing was responsible for the observed effect? Strength of the Manipulation A general principle to follow is to make the manipulation as strong as possible a strong manipulation maximizes the differences between groups and increases the chance that the independent variable will have a statistically significant effect on the dependant variable. A strong manipulation is most important in the early stages of research when you are trying to establish that a relationship does in fact exist at all. If the early experiments reveal a relationship, subsequent studies can systematically manipulate other levels of the independent variable to provide a more detailed picture of the relationship The principle of using the strongest possible strength of manipulation should be tempered by at least two things: 1. the strongest possible manipulation may involve a situation that rarely, if ever, occurs in the real world. Eg. An extrem
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