How psychologists do research

2 How psychologists do research

2 What makes psychological research scientific? Precision Skepticism Reliance on empirical evidence Willingness to make “risky predictions” Openness

2 Precision Theories Organized systems of assumptions that purport to explain phenomena and their interrelationships Hypotheses Attempt to predict or account for a set of phenomena; specify relationships among variables, and are empirically tested Operational definitions Specify how the phenomena in question are to be observed or measured

2 Critical thinking guidelines

2 Skepticism Scientists do not accept ideas on faith or authority. Skepticism means treating conclusions, both old and new, with caution.

2 Reliance on empirical evidence A scientist relies on empirical evidence to determine whether a hypothesis is true.

2 Willingness to make risky predictions Principle of falsifiability A scientific theory must make predictions specific enough to confirm and/or disconfirm the theory. The theory must predict not only what will happen, but also what will not happen. Confirmation bias Tendency to look for or attend to only information that confirms one’s own belief.

2 Openness Scientists must be willing to tell others where they got their ideas, how they tested them, and what the results were. Peer review, publishing and replicating research, gives science a built-in system of checks and balances.

2 Descriptive methods Methods that yield descriptions of behavior, but not necessarily causal explanations Include Case studies Observational studies Psychological tests Surveys

2 Case studies A detailed description of a particular individual being studied or treated, which may be used to formulate broader research hypotheses Most commonly used by clinicians; occasionally used by researchers

2 Observational studies Researchers carefully and systematically observe and record behavior without interfering with behavior Naturalistic observation Purpose is to observe how people or animals behave in their natural environments. Laboratory observation Purpose is to observe how people or animals behave in a more controlled setting.

2 Psychological tests Procedures used to measure and evaluate personality traits, emotional states, aptitudes, interests, abilities, and values Psychological tests can be objective or projective. Characteristics of a good test include Standardization Reliability Validity

2 Standardization The test is constructed to include uniform procedures for giving and scoring the test. In order to score tests in a standardized way, an individual’s outcome or score is compared to norms. To establish norms, the test is given to a large group of people who are similar to those for whom the test is intended. By having norms or established standards of performance, we know who scores low, average, or high.

2 Reliability When constructing a test, the scores achieved on the test at one time and place should be consistent with the scores achieved at another time and place.

2 Validity The ability of a test to measure what it was designed to measure Content validity The test broadly represents the trait in question. Criterion validity The test predicts other measures of the trait in question.

2 Surveys Questionnaires and interviews that ask people about experiences, attitudes, or opinions Requires a representative sample Group of subjects, selected from the population for study, which matches the population on important characteristics such as age and sex Popular polls and surveys rely on volunteers

2 Volunteer bias Volunteers who participate may differ from those who did not volunteer.

2 Correlational study A descriptive study that looks for a consistent relationship between two phenomena Correlation A statistical measure of how strongly two variables are related to one another. Correlational coefficients can range from 0.0 – 1.0.

2 Variables Characteristics of behavior or experiences that can be measured or described by a numeric scale. Variables are manipulated and assessed in scientific studies.

2 Direction of correlations Positive correlations An association between increases in one variable and increases in another, or decreases in one variable and decreases in the other. Negative correlations An association between increases in one variable and decreases in another.

2 Your turn What kind of correlation is this? 1. Positive 2. Negative 3. No correlation

2 Scatterplots Correlations can be represented by scatterplots.

2 Your turn What kind of correlation is this? 1. Positive 2. Negative 3. No correlation

2 Explaining correlations Start with three variables (X, Y, Z) X might cause Y Y might cause X X might be correlated with Y, which alone causes Z Correlations show patterns, not causes.

2 An experiment A controlled test of a hypothesis in which the researcher manipulates one variable to discover its effect on another. An experiment includes variables of interest, control conditions, and random assignment.

2 Variables of interest Independent variables Variables the experimenter manipulates Dependent variables Variables the experimenter predicts will be affected by manipulations of the independent variable(s)

2 Your turn An experimenter wants to study the effects of music on studying. He has some students study while listening to music and others study in silence, and then compares their test scores. What is the independent variable in this experiment? 1. The students 2. The presence of music while studying 3. The kind of music 4. The test scores

2 Control conditions In an experiment, a comparison condition in which subjects are not exposed to the same treatment as in the experimental condition. In some experiments, the control group is given a placebo, an inactive substance or fake treatment.

2 Random assignment For experiments to have experimental and control groups composed of similar subjects, random assignment should be used. Each individual participating in the study has the same probability as any other of being assigned to a given group.

2 Experimenter effects Unintended changes in subjects’ behavior due to cues inadvertently given by the experimenter. Strategies for preventing experimenter effects include single- and double-blind studies.

2 Descriptive statistics Statistical procedures that organize and summarize research data Examples Arithmetic mean Standard deviation

2 Inferential statistics Statistical procedures that allow researchers to draw inferences about how statistically meaningful a study’s results are. The most commonly used inferential statistics are significance tests. Statistical tests that show how likely it is that a study’s results occurred merely by chance

2 Choosing the best explanation Interpretation of results may depend on how the research was conducted. Cross-sectional studies Subjects of different ages are compared at a single time. Longitudinal studies Subjects are periodically assessed over a period of time.

2 Judging the results’ importance Statistical techniques can help determine if results are really important. Effect size is the amount of variance among scores in the study accounted for by the independent variable. Meta-analysis is a procedure for combining and analyzing data from many studies. It determines how much of the variance in scores across all studies can be explained by a particular variable.

2 The ethics of studying humans Informed consent Prospective participants should receive enough information to let them decide freely whether to participate. Freedom to withdraw at any time Minimize discomfort Keep data confidential If deception is necessary, debriefing must occur

2 The ethics of studying animals Animals have always been used in a small percentage of psychological studies. To conduct basic research To discover practical applications To study issues that cannot be studied experimentally using human beings To clarify theoretical questions To improve human welfare

How psychologists do research