AP Psychology Unit 0.4, 0.5, 0.6

AP Psychology Unit 0.4, 0.5,

correlation

a measure of the extent to which two factors vary together, and thus of how well either factor predicts the other

correlation coefficient

a statistical index of the relationship between two variables (from −1.00 to +1.00)

variable

anything that can vary and is feasible and ethical to measure

scatterplot

a graphed cluster of dots, each of which represents the values of two variables. The slope of the points suggests the direction of the relationship between the two variables. The amount of scatter suggests the strength of the correlation (little scatter indicates high correlation).

illusory correlation

perceiving a relationship where none exists, or perceiving a stronger-than-actual relationship

regression towards the mean

the tendency for extreme or unusual scores or events to fall back (regress) toward the average

expirement

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

experimental group

in an experiment, the group exposed to the treatment — that is, to one version of the independent variable.

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 a 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.

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

factor that changes, who’s effect is being studied

dependent variable

factor that does not change, outcome that is measared

cofounding variable

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

expirementer bias

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

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 deceptions, to its participants

descriptive statistics

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

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

median

the middle score in a distribution; half the scores are above it and half are below it

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 measure 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

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 statistical 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.

null hypothesis

an assumption that no difference exists between groups

effect size

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