Chapter 14: Correlated Groups t-Test

Question 1

When do we use single sample t-test?

Answer 1

• mean of null hypothesis population is unknown

- usually only have the mean

Question 2

What are the limitations of single sample designs?(2)

Answer 2

• Usually mu is not known

- if u were known, cannot be certain if conditions under which mu was calculated are applicable.

Question 3

Characteristics of correlated groups designs?(2)

Answer 3

• Each subject used before conditions ( before and after) aka control and experimental .
• Pairs of subjects matched on one or more characteristic serve in both conditions.

Question 4

What is the information tested by correlated group design?(2)

Answer 4

• Difference scores:
• magnitude of difference scores
• direction of difference scores

Question 5

What are difference scores?

Answer 5

• random sample from a population of difference scores having a mean of zero!

Question 6

What is the formula for tobt for correlated groups?

Answer 6

• Dobt- uD/ Sd/>/N

or Dobt - uD/ >/ SSd/ N(N-1)

Question 7

What is the formula for SSd for correlated groups?

Answer 7

• SSd= ED^2 - (ED)^2/N

Question 8

List the steps to solving a correlated group question!

Answer 8

1. calculate differences from the before and after values, calculate D^2
2. Calculate the summation of D, summation of D^2
3. Calculate the Dobt= ED/N
4. Calculate SSd than Tobt
5. find df ( N-1)
6. evaluate the statistic based on its sampling distribution. ( look at alpha and use df, look at table D for tcrit )
7. Conclude

Question 9

Whats the conclusion for evaluation of the statistic?

Answer 9

• If | tobt | > | tcrit |, reject ho

Question 10

What is the calculation for Cohen’s D? (effect size)

Answer 10

• d= | Dobt |/ Sd
• Sd= standard deviation sample difference scores
• Dobt= value of mean of the sample difference scores
• d ? estimated d

Question 11

How do you solve for Sd?

Answer 11

Square root of: SSd/N-1