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

naturalistic observation
research method in which the psuchologist observes the subject in a natural setting without interfering

case study
research method that involves an intensive investigation of one or more participants

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

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

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

correlation
the measure of a relationship between two variables or sets of data

hypothesis
an educated guess about the relationship between two variables

variable
any factor that is capable of change

experimental group
the group to which an independent variable is applied

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

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

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

doubleblind experiment
an experiment in which neither the experimenter nor the 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 that from the actual treatment

statistics
the branch of mathematics concerned with summarizing and making meaningful inferences from collections of data

descriptive statistics
the listing and summarizing of data in a pratical, efficient way

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, bellshaped curve; a graph of normally distributed data

central tendency
a number that describes something about the "average" score of a distribution

variability
a measure of difference, or spread of data

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

inferential statistics
numerical methods used to determine whether research data support a hypothesis or whether results were due to chance

