Research Methods of Psychologists



Research Methods of Psychologists

Critical Thinking thinking that does not blindly accept arguments and conclusions

examines assumptions; discerns hidden values; evaluates evidence

Limits to critical thinking

Hindsight Bias -- tendency to believe, after learning an outcome, that one would have foreseen it (the “I-knew-it-all-along” phenomenon)

Overconfidence -- we tend to think we know more than we do

Research Strategies

Theory -- an explanation using an integrated set of principles that organizes and predicts observations

Hypothesis -- a testable prediction (often implied by a theory)

Replication -- repeating the essence of a research study to see whether the basic finding generalizes to other subjects and circumstances; usually with different subjects in different situations

False Consensus Effect -- tendency to overestimate the extent to which others share our beliefs and behaviors

Confirmation bias – Researchers look for results that confirm their hypothesis

Types of Research Studies

Case Study -- an observation technique in which one person is studied in depth in the hope of revealing universal principles

Survey -- technique for ascertaining the self-reported attitudes or behaviors of people, usually by questioning a representative, random sample of them

Naturalistic Observation -- observing and recording behavior in naturally occurring situations without trying to manipulate and control the situation

Correlation -- a statistical measure that indicates the extent to which two factors vary together and thus how well either factor predicts the other

Problem: Illusory Correlation -- the perception of a relationship where none exists

Experiment -- a research method in which the investigator manipulates one or more factors (independent variables) to observe their effect on some behavior or mental process (the dependent variable)

while controlling other relevant factors by random assignment of subjects

Experimental Condition -- the condition of an experiment that exposes subjects to the treatment, that is, to one version of the independent variable

Control Condition -- the condition of an experiment that contrasts with the experimental treatment serves as a comparison for evaluating the effect of the treatment

Random Selection – a method of choosing participants for the study from the population. Can pick out of a hat, or generate a list of random numbers and have a computer choose the subjects.

Random Assignment -- assigning subjects to experimental and control conditions by chance (minimizes pre-existing differences between those assigned to the different groups)

Independent Variable -- the experimental factor that is manipulated (the variable whose effect is being studied)

Dependent Variable -- the experimental factor that may change in response to manipulations of the independent variable (in psychology it is usually a behavior or mental process)

Confounding Variable – any variable that is not controlled that can interfere with the reliability of the study

Operational Definition -- a statement of the procedures (operations) -- used to define research variables

Placebo – a substance or condition that may be administered instead of a presumed active agent, such as a drug, to see if it triggers the effects believed to characterize the active agent

Double-blind procedure -- an experimental procedure in which both the subject and the research staff are ignorant (blind) about whether the subject has received the treatment or a placebo

**commonly used in drug-evaluation studies

Descriptive Statistics

Measures of central tendency

Mean – average score

Mode – most frequent score

Median – middle score

Measures of relationships

Correlation coefficient – ranges from -1.00 to 1.00

Positive correlation – both measures go in same direction (ex. As height increases, weight increases)

Negative correlation – measures go in opposite direction (ex. As caffeine levels rise, calmness falls)

Plotting data

Normal curve – Bell-shaped curve - typical distribution of any set of scores

Skewed distribution – unusual distribution of scores with a spike of scores on one end of the distribution (skewed right – spike is at left, skewed left – spike is at right)

Measures of variability

Range – difference between high and low scores in the distribution

Standard deviation – based on normal curve, measure of the average distance of each score from the mean score. If S.D. is small, scores will be close together (the average distance from the mean is very small). 68% of the scores fall between one standard deviation on each side of the mean; 95% fall within two standard deviations on each side of the mean; 99.7% fall within three standard deviations on each side of the mean.

Variance = standard deviation squared

Inferential statistics

Statistical significance – chance that results would occur randomly – commonly must meet 5% threshold (Alpha level or p ................
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