Lecture 6E: T-tests Flashcards
What does an Independent t-test assess?
Test whether there is a difference in means between two independent groups/means.
Provide an example of when independent t-test would be used.
Comparing the average blood pressure of patients in a treatment group versus a control group.
What formula is used to calculate the t score in an Independent t-test?
t score = (mean1 - mean2) / (within-group variability)
What factors increase the t score in an Independent t-test?
- ↑ between-group variability (difference in means)
- ↓ within-group variability (SD in each group)
- ↑ sample size
If t-score increases, what happens to the p value?
- More likely to find a significant difference
- Higher likelihood to reject null hypothesis
What is a Paired t-test used for?
Test the difference between two paired or related means, e.g. measurements taken from the same subjects under two different conditions
Provide an example of when a Paired t-test might be used.
The heart rate measured at two different times (before and after treatment).
What does a p-value less than 0.05 indicate in hypothesis testing?
Reject the null hypothesis.
What is a Two-tailed (non-directional) Test?
Test for differences in both directions, e.g. interested in knowing whether PT students are taller or shorter than OT students
What is a One-tailed (directional) Test?
Test for differences in only one direction, e.g. is life expectancy less for smokers than for non-smokers?
What happens if you find no significant difference in a two-tailed test?
You cannot switch to a one-tailed test later: unethical.
What is the significance of the area under the t-distribution in Two-tailed Tests?
Total area under the t-distribution is split between both tails.
If α2=0.05, each distribution is 0.025
What statistical test would be appropriate to compare systolic blood pressure before and after a test?
Paired t-test.
If the p-value obtained for cognitive function comparison is 0.09, what should be the interpretation?
Do not reject the null hypothesis. There is no significant difference in cognitive function between the two populations.
