W3(2) Flashcards
(34 cards)
What is the goal in a paired sample t-test?
To see if there’s a significant difference in the same group at different times or under different conditions.
What is another example of using a paired t-test?
Comparing satisfaction with the company vs. satisfaction with the department — same participants, different variables.
What is an independent sample t-test used for?
To compare mean scores of two different groups of people on the same metric.
What’s the difference between paired and independent t-tests?
Paired: same people, 2 times; Independent: different groups of people.
What are the hypotheses for an independent t-test?
H0: Mean difference = 0, H1: Mean difference ≠ 0 (or greater than / less than)
What assumptions do we need for this test?
The variable should be normally distributed and we test for equal variances.
What test checks if variances are equal?
Levene’s Test.
What happens if Levene’s Test is significant?
Variances are unequal — use Welch t-test.
What if Levene’s Test is not significant?
Variances are equal — use 2 sample t-test.
Give an example scenario for an independent t-test.
Comparing if seeing a cynical humour ad affects attitudes toward Colgate vs. a group that didn’t see the ad.
What does the R function for Welch look like?
t.test(df$Attitude_Colgate ~ factor(df$group)) if unequal variances.
What does a significant p-value mean in an independent t-test?
That there is a statistically significant difference between the two groups.
What if the result is opposite to the hypothesis?
reject null, fail to reject alternative hypothesis
When do you use a one-sided t-test?
If you expect the difference to be in one direction (e.g., one group will have higher scores than the other).
What is the purpose of a one-way ANOVA?
To compare mean scores of more than 2 different groups of people or conditions on a particular metric.
What assumptions must be met for ANOVA?
Variables must be normally distributed.
What is the hypothesis for one-way ANOVA?
H0: Means of all groups are equal, H1: At least one group mean is different
How do we interpret variance in ANOVA?
If group means are close (low between-group variance), F is low. If group means are far apart (high between-group variance), F is higher.
Give a practical example of using ANOVA.
A manager tests whether 3 training levels (beginner, intermediate, advanced) affect how fast employees solve a problem.
What do we do after a significant ANOVA result?
Use Tukey HSD to see which groups actually differ.
What does the Tukey HSD test do?
It compares all possible group pairs to tell us which specific group differences are significant.
How do you interpret p-values in Tukey HSD output?
If p adj < 0.05, the groups are significantly different. If p adj > 0.05, they are not.
What did the Tukey test show in the training example?
Beginners took significantly longer than advanced. Intermediate and advanced were not significantly different.
What does correlation analysis measure?
The direction and strength of the linear relationship between two numerical paired values.
