PSYC 2010 – t-Tests & Research Design Vocabulary

These vocabulary flashcards cover key statistical and methodological concepts from the lecture notes on conducting and interpreting t-tests in psychology research.

t-test

A statistical procedure that compares the means of exactly two groups on an interval/ratio dependent variable to determine if a significant difference exists.

Independent Variable (IV)

The variable that creates the two groups/conditions being compared in a t-test; may be manipulated (experimental) or naturally occurring (quasi-experimental).

Dependent Variable (DV)

The interval or ratio-level outcome measured and compared across the two groups in a t-test.

Independent Samples t-test

A between-subjects t-test used when different participants belong to each of the two groups being compared.

Dependent Samples t-test

A within-subjects t-test used when the same participants take part in both conditions being compared.

Between-Subjects Design

Research design in which each participant appears in only one condition; required for an independent samples t-test.

Within-Subjects Design

Research design in which the same participants experience both conditions; required for a dependent samples t-test.

Homogeneity of Variance

The assumption that the two groups in an independent t-test have equal variances.

Levene’s Test

A statistical test reported in SPSS that evaluates the homogeneity of variance assumption for an independent samples t-test.

Experimental Design

A study design in which the IV is actively manipulated by the researcher, allowing causal inference when using a t-test.

Quasi-Experimental Design

A study design in which the IV is not manipulated but represents pre-existing or naturally occurring groups compared with a t-test.

Degrees of Freedom (df)

A value linked to sample size (n-2 for an independent t-test) that is reported in parentheses with the t statistic.

95% Confidence Interval

The range of values in which the true mean difference is expected to lie with 95% certainty, reported alongside t-test results.

Effect Size (r)

A measure of practical importance for a t-test, calculated as √(t²/(t² + df)); interpreted as small (.10), medium (.30), or large (.50).

APA Style Reporting

Standard format for presenting t-test results: t(df) = value, p value, followed by means (M) and standard deviations (SD).

One-Sided p-value

The probability associated with a directional hypothesis in a t-test (testing whether one mean is specifically greater than the other).

Two-Sided p-value

The probability associated with a non-directional hypothesis in a t-test (testing for any difference between means).

Mean (M)

The arithmetic average score for each group, reported to two decimal places in APA style.

Standard Deviation (SD)

A measure of variability within a group, accompanying the mean in APA reporting.

Standard Error Mean (SEM)

An estimate of how much the sample mean would vary across repeated samples; SD divided by the square root of n.

Background Sound Experiment

Study in which students either studied with constant background sound or in silence before taking a 100-point test.

Group Statistics

SPSS output table listing n, mean, SD, and SEM for each group prior to the t-test.

SPSS

Statistical software used to enter data, run t-tests, and produce outputs such as Levene’s test and Independent Samples Test tables.