4. T-tests

Question 1

What are the three assumptions of a parametric test? (T-tests methods 2)

Answer 1

Normally distributed data
Data is interval or ratio
Groups do not show homogeneity of variance

Question 2

What is a dependent t-test? (T-tests methods 2)

Answer 2

Same subjects do all conditions

e.g repeated measures

Question 3

What is an independent t-test? (T-tests methods 2)

Answer 3

Different participants do different conditions

Question 4

How do you work out the dependent t-test? (T-test methods 2)

Answer 4

1) Find the differences, per group, with the changing conditions
2) Add these differences up and divide by number of groups
3) Take each difference away from this mean
4) Square each of the numbers
5) Find the sum of the squares
6) Variance divided by the number of participants SQRT
7) Compare findings to critical values

Question 5

What is the variance for dependent t-tests? (T-test methods 2)

Answer 5

sum of squares divided by the DOF

Question 6

What is the DOF for dependent t-tests? (T-test methods 2)

Answer 6

Number of participants minus 1

Question 7

How do you work out the independent t-test? (T-test methods 2)

Answer 7

1) Find the individual sum of the mean scores of group A and then group B
2) For each score, take away the group mean for group A and then group B
3) Square these number for group A and then group B
4) Find the sum of squares for group A and then group B
5) Find the degrees of freedom
6) Find the variance

Question 8

What is the DOF for independent t-tests? (T-test methods 2)

Answer 8

(group 1 - 1) + (group 2 - 1) = DOF