The t Test for Two Independent Samples

Flashcards for reviewing key concepts related to the independent-measures t test and its application in hypothesis testing.

Independent-Measures t Test

A hypothesis test that uses two separate samples to evaluate the mean difference between two treatment conditions or populations.

Pooled Variance

A combined estimate of variance from two or more samples, used in the independent-measures t test to compute the estimated standard error.

Degrees of Freedom (df)

The number of independent values that can vary in an analysis; for independent measures t test, it is calculated as df = n1 + n2 - 2.

Sampling Error

The error that occurs when a sample is used to estimate a population parameter; it can lead to differences between sample means that are not representative of true population differences.

Null Hypothesis (H0)

The hypothesis stating that there is no effect or no difference between populations or treatment means.

Alternative Hypothesis (H1)

The hypothesis asserting that there is a statistically significant effect or difference between populations or treatment means.

Critical Region

The range of values for a test statistic that leads to rejection of the null hypothesis in a hypothesis test.

Mean Difference (MD)

The difference between the means of two groups; it is used to evaluate whether observed differences are statistically significant.

Effect Size (Cohen's d)

A measure of the magnitude of a treatment effect, calculated as the difference between two means divided by the pooled standard deviation.

Independent Measures Design

A research design in which different participants are used in each group of a study.

Repeated Measures Design

A research design in which the same participants are used in all treatment conditions.

Within-Treatments Variance (MSwithin)

The average variance of scores within treatment groups, used in the denominator of the F-ratio in ANOVA.

Between-Treatments Variance (MSbetween)

The average variance of the differences between treatment group means, used in the numerator of the F-ratio in ANOVA.

Tukey’s HSD Test

A post hoc test used to find which specific means are significantly different after an ANOVA has indicated that significant differences exist.

F-Ratio

A ratio of variances calculated in ANOVA; it compares the variance between treatment means to the variance within treatment groups.

Type I Error

The error of rejecting the null hypothesis when it is in fact true.

Confidence Interval (CI)

A range of values derived from the sample that is believed to contain the population parameter with a certain level of confidence.

Sampling Distribution

The probability distribution of a statistic obtained through a large number of samples drawn from a specific population.

Estimated Standard Error (sM)

An estimate of the variability of a sample mean from the population mean, calculated from the sample variance and size.