AP Psych: Unit 0 Vocabulary Cont'd

Control group

In an experiment, the group not exposed to the treatment contrasts with the experimental group and serves as a comparison for evaluating the effect of the treatment.

Random assignment

Assigning participants to experimental and control groups by chance, thus minimizing preexisting differences between the different groups.

Single-blind procedure

An experimental procedure in which the research participants are ignorant (blind) about whether they have received the treatment or placebo.

Double-blind procedure

An experimental procedure in which both the research participants and the research staff are ignorant (blind) about whether the research participants have received the treatment or a placebo. Commonly used in drug-evolution studies.

Placebo effect

Experimental results caused by expectations alone; any effect on behavior caused by the administration of an inert substance or condition, which the recipient assumes is an active agent.

Independent variable

In an experiment, the manipulated factor is the variable whose effect is being studied.

Confounding variable

In an experiment, a factor other than the factor being studied that might influence a study’s results.

Experimenter bias

Bias caused when researchers may unintentionally influence results to confirm their own beliefs.

Dependent variables

In an experiment, the outcome that is measured. The variable that may change when the independent variable is manipulated.

Validity

The extent to which a test or experiment measures or predicts what it is supposed to.

Quantitative research

A research method that relies on quantifiable, numerical data.

Qualitative research

A research method that relies on in-depth, narrative data that are not translated into numbers.

Informed consent

Giving potential participants enough information about a study to enable them to choose whether they wish to participate.

Debriefing

The post-experimental explanation of a study, including its purpose and any deception, to its participants.

Histogram

A bar graph depicting a frequency distribution.

Mode

The most frequently occurring score(s) in a distribution.

Mean

The arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores.

Percentile rank

The percentage of scores that are lower than a given score.

Skewed distribution

A representation of scores that lack symmetry around their average value.

Range

The difference between the highest and lowest scores in a distribution.

Standard deviation

A computed meaure of how much scores vary around the mean score.

Normal curve

A symmetrical, bell-shaped curve that describes the distribution of many types of data; most scores fall near the mean (about 68% fall within one standard deviation of it), and fewer and fewer scores lie near the extremes. (Also called a normal distribution).

Inferential statistics

Numerical data that allow one to generalize—to infer from sample data the probability of something being true of a population.

Meta-analysis

A statistical procedure for analyzing the results of multiple studies to reach an overall conclusion.

Statistical significance

A significance statement of how likely it is that a result (such as a difference between samples) occurred by chance, assuming there is no difference between the populations being studied.

Effect size

The strength of the relationship between two variables. The larger the effect size, the more one variable can explain the other.

Descriptive statistics

Numerical data used to measure and describe characteristics of groups; include measures of central tendency and measures of variation.