11. Comparing Means

Question 1

What is the T-test used for?

Answer 1

to assess whether two group means are different

Question 2

IVs and DVs in the t-test

Answer 2

only 1 IV

only 1 DV

Question 3

t-test statistic equation

Answer 3

t-test = (model ÷ error)

Question 4

two types of t-test

Answer 4

• independent means t-test

- dependent means t-test

Question 5

When do you use an independent means t-test?

Answer 5

• 2 experimental conditions

- different participants assigned to each condition

Question 6

What is the independent means t-test also called?

Answer 6

• independent samples

- unpaired

Question 7

What must you acknowledge with an independent means t-test?

Answer 7

unsystematic variance

Question 8

How do you use the independent means t-test score?

Answer 8

• compare value of t against the max value that would be expected to have by chance alone in a t-distribution with same df

Question 9

What happens if the t-stat is more than the critical value in an independent means t-test?

Answer 9

results are due to the effect of the IV and not by chance alone

Question 10

When do you use the dependent means t-test?

Answer 10

same group of people are exposed to different treatments or are assessed before and after an intervention

Question 11

dependent means t-test and experimental conditions

Answer 11

• 2 experimental conditions

- same participants take part in both

Question 12

dependent means t-test is also called

Answer 12

• dependent samples

- paired t-test

Question 13

How do you use the dependent means t-test score

Answer 13

• calculate t-test stat and compare against the max value that would be expected to have occurred by chance alone in a t-distribution with the same df

Question 14

What is the critical value?

Answer 14

max value that would be expected to have occurred by chance alone

Question 15

If the t-stat is more than the critical value, results are due to

Answer 15

the effect of the IV and not by chance alone

Question 16

Assumptions for independent t-tests

Answer 16

• normally distributed
• interval data
• homogeneity of variance
• independence

Question 17

Assumptions for dependent t-tests

Answer 17

• normally distributed

- interval data

Question 18

degrees of freedom

Answer 18

• number of observations that are free to vary

- 1 less than the sample size

Question 19

What are your 3 options if the data isn’t normally distributed?

Answer 19

• use a larger sample
• transform the distribution
• use non-parametric tests