Week 12

Which of the following is not a step or assumption in carrying out an independent groups t-test?

• a. estimating the variance of the population of the distribution of differences between means

• b. assuming the population is normal

• c. estimating the standard deviation (standard error) of the distribution of the difference between the means

• d. assuming there is no correlation between score pairs for the two conditions of the study

• e. summing the z-score products

Read the following, and write down any important information:

A computer software company wishes to know whether Microsoft’s Word is better than Apple’s Pages. Eight equally proficient microcomputer operators are randomly divided into two equal groups. One group is given Word and the other is given Pages. The mean time to produce perfect copies of the same document is 52 minutes for the group using Word and 44 minutes for the group using Pages. The sums of squares for Word is 22 and for Pages, it is 26.

• a. Click me when you've got all the information :)

• b

What is the research design?

• a. independent groups

• b. matched subjects

• c. repeated measures

• d. a mixture of a and b

• e. non-experimental (observation)

What is the measurement scale for the dependent variable?

• a. at least ordinal and possibly interval

• b. at least interval and possibly ratio

• c. definitely ratio

• d. definitely nominal

• e. definitely interval and not ratio

What type of measure is being taken?

• a. self-report/rating

• b. behavioural

• c. physiological

• d. self-report/forced-choice

• e. self-report/semantic differential

■What are the two independent estimates of the population variance?

• a. 6.17 and 6.89

• b. 7.33 and 8.66

• c. 6.99 and 7.13

• d. 7.34 and 8.52

• e. 12.65 and 14.68

What is the pooled variance in this example?

• a. 4

• b. 8

• c. 12

• d. 16

• e. 96

What is the variance of each of the two distributions of means?

Hint: They have the same N so they’ll be the same value!

• a. 1

• b. 2

• c. 6

• d. 8

• e. 3

What is the standard deviation of the distribution of differences between means?

• a. 0.86

• b. 0.93

• c. 2.00

• d. 2.62

• e. 4.00

Adopting a significance level of 5%, what is the critical value of t for the t test?

• a. 2.447

• b. 2.365

• c. 1.943

• d. 1.895

• e. 2.145