Question

1. What does the paired-samples t-test test for?

2. The paired-samples t-test utilizes a within-subjects design. What is the main difference between a within-subjects design and a between subjects design?

3. What is the difference between a repeated measures and a matched design?

Answer 1

1.The Paired Samples t Test compares two means that are from the same individual, object, or related units.

The purpose of the test is to determine whether there is statistical evidence that the mean difference between paired observations on a particular outcome is significantly different from zero.

2.Within subject variation in an experiment refers to the variation seen in a group of subjects which are all treated the same way. If a doctor is testing three medicines to look for a difference in their effectiveness, and is also interested in differences between genders, she might separate male subjects into three groups and treat each with a different medicine, then do the same with three female groups. Even within one group of subjects (same gender, same medicine), however, different patients will have different responses. This is the within subject variation.

Between subject design

This is the difference between different groups exposed to different factors. In the example of the doctor's tests, she would look at the difference in average recovery time between male and female groups and also between each of the groups taking one of the three medicines. In each case, there will likely be differences between the groups. The task of the designed experiment is to see if this difference is statistically significant.

A dependent t-test is an example of a "within-subjects" or "repeated-measures" statistical test. This indicates that the same participants are tested more than once. Thus, in the dependent t-test, "related groups" indicates that the same participants are present in both groups

3.

In a repeated measures design, each group member in an experiment is tested for multiple conditions over time or under different conditions.For example, a group of people with Type II diabetes might be given medications to see if it helps control their disease, and then they might be given nutritional counseling. A blood test to measure glucose levels is given to the patients after each treatment.

Matched subject design

Matched-subjects designs use different participants in each group, but the participants have been closely matched before assignment to conditions. The characteristics are:

1. Each participant is exposed to only one level of the independent variable.
2. Each participant has a matched participant in each of the other conditions, so the groups are correlated.
3. Only one measurement per participant on the dependent variable is used, and the analysis takes into account the matching.
4. The critical comparison is the difference between the correlated groups.