PSYC 2317: Statistical Methods in Psychology Ch. 1

statistics

refers to a set of mathematical procedures for organizing, summarizing, and interpreting information.

population

the set of all the individuals of interest in a particular study.

sample

a set of individuals selected from a population, usually intended to represent the population in a research study.

random sample

everyone in the population has an equal chance of being selected.

variable

a characteristic or condition that changes or has different values for different individuals.

Data (plural)

measurements or observations.

data set

a collection of measurements or observations.

A datum (singular)

a single measurement or observation and is commonly called a score or raw score.

parameter

a value, usually a numerical value, that describes a population. It is usually derived from measurements of the individuals in the population.

statistic

a value, usually a numerical value, that describes a sample. It is usually derived from measurements of the individuals in the sample.

Descriptive statistics

statistical procedures used to summarize, organize, and simplify data.

Inferential statistics

consist of techniques that allow us to study samples and then make generalizations about the populations from which they were selected.

Sampling error

the naturally occurring discrepancy, or error, that exists between a sample statistic and the corresponding population parameter.

Constructs

internal attributes or characteristics that cannot be directly observed but are useful for describing and explaining behavior.

operational definition

identifies a measurement procedure (a set of operations) for measuring an external behavior and uses the resulting measurements as a definition and a measurement of a hypothetical construct. Note that an operational definition has two components. First, it describes a set of operations for measuring a construct. Second, it defines the construct in terms of the resulting measurements.

discrete variable

consists of separate, indivisible categories. No values can exist between two neighboring categories.

continuous variable

divisible into an infinite number of fractional parts.

Real limits

the boundaries of intervals for scores that are represented on a continuous number line. The ___________ separating two adjacent scores is located exactly halfway between the scores. Each score has two _________.

upper real limit

at the top of the interval.

lower real limit

at the bottom of the interval.

nominal scale

consists of a set of categories that have different names. Measurements on a _________ label and categorize observations, but do not make any quantitative distinctions between observations.

ordinal scale

consists of a set of categories that are organized in an ordered sequence. Measurements on an __________ rank observations in terms of size or magnitude.

interval scale

consists of ordered categories that are all intervals of exactly the same size. Equal differences between numbers on a scale reflect equal differences in magnitude. However, the zero point on an ___________ is arbitrary and does not indicate a zero amount of the variable being measured.

ratio scale

an interval scale with the additional feature of an absolute zero point. With a _______, ratios of numbers do reflect ratios of magnitude.

Descriptive research or the descriptive research strategy

involves measuring one or more separate variables for each individual with the intent of simply describing the individual variables.

correlational method

two different variables are observed to determine whether there is a relationship between them.

independent variable

the variable that is manipulated by the researcher. In behavioral research, the _______________ usually consists of the two (or more) treatment conditions to which subjects are exposed. The _________ is manipulated prior to observing the dependent variable.

dependent variable

the one that is observed to assess the effect of the treatment. The ____________is the variable that is measured in the experiment and its value changes in a way that depends on the status of the independent variable.

control condition

Individuals in a _______________do not receive the experimental treatment. Instead, they either receive no treatment or they receive a neutral, placebo treatment. The purpose of a ___________ is to provide a baseline for comparison with the experimental condition.

experimental condition

Individuals in the __________ do receive the experimental treatment.

nonequivalent groups study

score comparison method where the researcher does not control which participants go into which group

pre-post study

method of using the passage of time to create the groups of scores.

quasi-independent variable.

In a nonexperimental study, the "independent variable" that is used to create the different groups of scores is often called the_______.