L3: REPEATED T-TEST

Question 1

Who developed the t-test and why is it called “Student’s” t-test?

Answer 1

William Sealy Gosset developed it in 1908 for small samples. He published under the name “Student,” so it’s called Student’s t-test.

Question 2

What is the purpose of a t-test?

Answer 2

To test whether there are significant differences between means in one or two groups.

Question 3

What are the three main types of t-tests?

Answer 3

1. One-sample t-test – compares one group to a known value
2. Independent samples t-test – compares two separate groups
3. Paired samples t-test – compares two related or matched sets of scores

Question 4

What is the t statistic based on, and what affects its accuracy?

Answer 4

It’s based on sample variance, which requires the sample mean. Accuracy improves as sample size and degrees of freedom (df) increase

Question 5

How does degrees of freedom (df) affect the t distribution?

Answer 5

As df increases, the t-distribution more closely approximates the normal distribution, and the critical value of t decreases.

Question 6

What are the key assumptions of parametric tests?

Answer 6

1. Normality – Data should be normally distributed
2. Equal variance – Groups should have similar variance
3. Independence – Samples must be random and independent
4. No outliers – Extreme values should be absent
5. Interval level data – Data should be at least interval scale

Question 7

What are the advantages of a repeated measures design?

Answer 7

Reduces participant variables (individual differences)
Requires fewer participants

Question 8

What are the disadvantages of a repeated measures design?

Answer 8

Order effects (can be controlled with counterbalancing)
Practice effects like boredom or fatigue

Question 9

What is the difference between H₀ and H₁ in hypothesis testing?

Answer 9

H₀ (null hypothesis): Assumes no effect or difference (e.g., mean difference = 0)
H₁ (alternative hypothesis): Assumes there is an effect of the IV on the DV

Question 10

What are the assumptions of a paired samples t-test?

Answer 10

DV is continuous
IV has 2 related/matched groups
Differences between pairs are approximately normal
No significant outliers in the difference scores

Question 11

How do we calculate a paired samples t-test?

Answer 11

Sum of differences
Over
Number of participants

Question 12

Whats the hypothesis for one sample t-test?

Answer 12

Null hypothesis: The sample mean equals the population mean.

Alternative hypothesis: the sample mean is different then the population mean