Identify the test
A psychologist compares stress levels of nurses working day shifts versus night shifts. Each nurse works only one shift.
Independent samples t-test
Within or between-subjects? Participants complete a reaction time task once in silence and once while listening to music.
Within
In ANOVA, what does within-groups variance primarily represent?
Random error and individual differences
What are the three primary assumptions of ANOVA?
Normality, homogeneity of variance (all pops have the same variance), and independence
In a one-sample t test with n = 12, what are the degrees of freedom?
11
A researcher measures participants’ blood pressure before and after an 8-week exercise program.
Paired-samples t test
Within or between-subjects? Researchers compare depression scores between students who own pets and students who do not.
Between-subjects
What happens to the F statistic if between-groups variance increases while within-groups variance stays the same?
F increases
Which ANOVA assumption is most serious if violated?
Independence
In an independent-samples t test with n₁ = 15 and n₂ = 17, what are the degrees of freedom?
30
A cereal company wants to know if the average sugar content in its cereal differs from the advertised 12 grams per serving.
One-sample t test
Between or within-subjects? A researcher measures pain tolerance in the same participants across three temperatures (cold, lukewarm, hot).
Within-subjects
If the null hypothesis is true, how should between-groups variance compare to within-groups variance?
They should be approximately equal
Why is violating independence especially problematic?
It inflates Type I error, invalidates the p-value
A researcher conducts 4 pairwise comparisons and uses Bonferroni correction. What is the adjusted alpha?
.0125
A professor compares average GPA across freshmen, sophomores, juniors, and seniors.
ANOVA
Between or within-subjects? In which design are individual differences most likely to inflate error variance?
Between-subjects
If scores within each group are very spread out, what happens to within-groups variance?
It increases
After a significant omnibus F test, what must be conducted to determine where differences exist?
Post hoc tests/pairwise comparisons
If a study reports t(18) = 2.31, what does 18 represent?
Degrees of freedom
A researcher compares memory performance across four different noise conditions. Participants are randomly assigned to one condition only.
ANOVA
Between or within-subjects? Researchers test participants’ problem-solving ability after drinking water, after drinking coffee, and after drinking an energy drink. Each participant completes all three conditions on separate days. What type of research design is being used?
Within-subjects
What two variance estimates are compared in the F ratio?
Between-groups variance and within-groups variance
Why is the F test called an omnibus test?
It tests the overall null hypothesis that all means are equal
If p = .03 and α = .05, what is the correct decision regarding the null hypothesis?
Reject the null