Research Design and Statistics Flashcards
True experimental research
At least one IV is manipulated and subjects are randomly assigned.
Quasi-experimental research
One IV manipulated, but no random assignment of subjects, typically because they’re already in groups.
Between groups design
Only compares groups that are independent. Ex: differences in reading levels of two different classes of second graders.
Within subjects design
Subjects are repeatedly measured. Ex: Looking at people’s ability to recall nouns/verbs/nonsense; all subjects are given the list of words to remember.
Analogue research
Evaluates treatment conditions that only resemble or approximate clinical situations.
Cross-sectional research
Looks at differences across sections (e.g., different ages) by sampling subjects from the age categories of interest at one point in time.
ex: How much time someone spends on the internet in groups of persons from different ages.
Longitudinal research
following a group of subjects over many years in order to understand the changes that take place as people age.
Simple random sampling
every member of the population has an equal chance of being selected.
Stratified random sampling
Population is first divided into strata (age, levels of income) and then random sample from each stratum is selected.
Threats to internal validity - History
Specific incidents that intervene between measuring points, either in or out of the experimental situation.
EX: An earthquake occurring right before implementation of a preparedness course.
Threats to internal validity - Maturation
Factors that affect the subjects’ performance because of the passing of time.
Threats to internal validity - Test practice
Familiarity with testing affects scores on repeated testing.
Threats to internal validity - Instrumentation
Changes in observers or the calibration of equpiment.
Threats to internal validity - Statistical regression
Regression to the mean; extreme scores tend to become less extreme over time.
Threats to internal validity - Selection bias
Caused by non-random assignment.
EX: if the first 20 subjects who volunteer for a study are assigned to one Tx, the next 20 to another, then we have selection bias.
Threats to internal validity - Diffusion
Occurs when the no-treatment group actually gets some of the treatment.
EX: Inadvertently having a discussion about cognitive strategies in a control group.
Construct Validity
Actually measuring what you intend to.
Threats to construct validity - Attention & Contact with Clients
Hard to tell whether the change in clients is due to the intervention or the attention/contact.
Threats to construct validity - Experimenter Expectancies
Cues/clues transmitted to the subjects by the experimenter ultimately affecting the data.
Rosenthal effect.
Threats to construct validity - Demand characteristics
Factors in the procedures that suggest how a subject should behave.
Threats to construct validity - John Henry Effect
Compensatory rivalry. Persons in the control group try harder than usual in the spirit of competition.
Threats to external validity - Contextual characteristics
Conditions in which the intervention is imbedded. Reactivity occurs when subjects behave in a certain way just because they are participating in research and being observed.
Standard deviation
Average deviation from the mean in a given set of scores. Square root of the variance.
Sampling error
samples drawn from populations are usually not perfectly representative of the population.
Central limit thoerem
Assuming an infinite number of equal sized samples are drawn from a population, the means will be normally distributed.
Type I error
rejecting the null when it’s really a mistake; significance is found but subsequent research finds no significance.
most likely in t-tests
Type II error
Accepting the null when you should reject it; significance is not found in original EXP, but subsequent studies find significance.
Power
Defined as ability to correctly reject the null.
Coefficient of determination
Squaring the correlation coefficient. Represents the amount of variability in Y that is shared with, xplained by, or accounted for by X.
EX: r = .5; coeff of det: .25. 5% of variability in Y is explained by X.