T test
What assumptions are made with a t-test?
Assumptions of normal distribution if a parametric tests is used. Otherwise a non parametric test should be used.
How are t-tests interpreted?
For the t test a t statistics is found from a t table. To find the t statistics you need the degrees of freedom (for a t test the degrees of freedom are found from the sum of persons in both groups minus 2). The confidence interval for the means should not include 0 if the null hypothesis is rejected as we are testing the hypotheses of difference between means in the sample.
How do we choose the type of t-test?
Look at distribution. Look at data is the data paired (same group before and after) in which case use a paired t-test. Is it two group one on placebo the other on a drug in which case the independent sample t-test is used.
What variables are analysed with a t-test?
The t-test is of a categorical nature e.g. it compares people within two groups (medication A vs placebo, before or after intervention). The dependent variable is a continuous interval or ratio.
When would you use a t-test?
The t-tests looks at the differences in two samples and examines their means relative to the spread or variablity of the scores. It is used when comparing within subjects (dependent sample) or between different subjects (independent sample).
