Statistical Tests Key

Comparing Means

  • Independent sample t-test: Compares the means of two groups on a DV in which

measurements of the two groups are independent

Predictor variable (IV or PV): Nominal

DV: Interval/ratio

Statistic: t

APA format t(df) = 3.42, p = .03

Report the means and standard deviations in each group

Plot with bar graph of means & error bars


  • Paired t-test: Compares the means of two groups on a DV in which measurements of the

two groups are linked

Predictor variable (IV or PV): Nominal

DV: Interval/ratio

Statistic: t

APA format t(df) = 3.42, p = .03

Report the means and standard deviations in each group

Plot with bar graph of means & error bars


  • 1- way ANOVA: Compares means of more than two groups on a DV (with two groups it

is equivalent to the t-test)

Can be independent or repeated measures

Predictor variable (IV or PV): Nominal

DV: Interval/ratio

Statistic: F

APA format F(df IV, df error) = 3.42, p = .03

Report the means and standard deviations in each group

May require follow-up post hoc tests if significant results for more than 2 conditions

Plot with bar graph of means & error bars


  • 2-way ANOVA: Compares the means on a DV for group differences when there are two

nominal predictor variables. Allows you to test for a main effect of IV1, a main effect of

IV2, and whether there is an interaction between the two IVs. Thus, there are three

results to report from a 2-way ANOVA. Each IV can be independent or repeated

measures.

Predictor variable (IV or PV) 1: Nominal

Predictor variable (IV or PV) 2: Nominal

DV: Interval/ratio

Statistic: F

APA format F(df IV, df error) = 3.42, p = .03

Report the means and standard deviations in each group

May require follow-up post hoc tests if significant results for more than 2 conditions

Plot with bar graph of means & error bars


Testing for Associations

  • Correlation: Tests the relationship between two variables that are both interval/ratio.

There is not necessarily a predictor variable and a dependent variable.

Statistic: r

APA format r = .34, p = .03

r ranges from -1 to 1

Report the range of data

Plot with scatterplot


  • Chi-square test: Tests the relationship between two variables that are nominal. There is

not necessarily a predictor variable and a dependent variable.

Statistic: X2

APA format X2 (df; N = 100) = 3.42, p = .03

N is total number of participants

Report the frequency of participants in each category (i.e., report the percentage of

participants in each group)

Plot with bar graph that has frequencies on Y-axis