- Chapter 2 vocabulary

### sample

the small group of participants, out of the total number available, that a researcher studies

### naturalistic observation

research method in which the psychologist observes the subject in a natural setting without interfering

### survey

research method in which information is obtained by asking many individuals a fixed set of questions

### longitudinal study

research method in which data is collected about a group of participants over a number of years to assess how certain characteristics change or remain the same during development

### cross-sectional study

research method in which data is collected from groups of participants of different ages and compared so that conclusions can be drawn about differences due to age

### control group

the group that is treated in the same way as the experimental group except that the experimental treatment (the independent variable) is not applied

### self-fulfilling prophecy

a situation in which a researcher's expectations influence that person's own behavior, and thereby influence the participant's behavior

### single-blind experiment

an experiment in which the participants are unaware of which participants received the treatment

### double-blind experiment

an experiment in which neither the experimenter nor the participants know which participants received which treatment

### placebo effect

a change in a participant's illness or behavior that results from a belief that the treatment will have an effect, rather than the actual treatment

### statistics

a branch of applied mathematics concerned with the collection and interpretation of quantitative data and the use of probability theory to estimate population parameters

### frequency distribution

an arrangement of data that indicates how often a particular score or observation occurs

### normal curve

a graph of frequency distribution shaped like a symmetrical, bell-shaped curve; a graph of normal distribution

### standard deviation

a measure of variability that describes an average distance of every score from the mean

### correlation coefficient

describes the direction and strength of the relationship between two sets of variables