I got most of these wrong and I don't understand why...I need to compare my answers.

1. In an independent groups experiment, if we must estimate the population standard deviation to determine the significance of the sample results, the appropriate inference test is the _________.

sign test

t test

z test

none of these

2. As the df increases, the t distribution _________.

gets more symmetrical

approaches the normal distribution

stays the same

3. The degrees of freedom for the t test for single samples are _________.

N

N - 1

N - 2

depends on alpha

4. How many t distributions are there?

1

2

30

one for each value of df

5. The mean of the t distribution equals _________.

0

1

N

N - 1

6. The power of the t test increases with _________.

increases in N

increases in the effect of the independent variable

decreases in the sample variance(s)

all of these

7. A correlated groups design is more sensitive than an independent groups design if _________.

there are large inter-subject differences

there are small inter-subject differences

the experimental treatment effect is strong

there is a high correlation between paired scores

8. One employs a correlated groups design _________.

to eliminate random error

to simplify calculations

for prediction

to reduce the effects of individual differences among subjects

9. If a test is a robust test,

it is sensitive to its underlying mathematical assumptions

it doesn't estimate any population parameters

it is insensitive to its underlying mathematical assumptions

it often may be used despite violations of its underlying mathematical assumptions

it is insensitive to its underlying mathematical assumptions and it often may be used despite violations of its underlying mathematical assumptions

10. A professor of women's studies is interested in determining if stress affects the menstrual cycle.Ten women are randomly sampled for an experiment and randomly divided into two groups.One of the groups is subjected to high stress for two months while the other lives in a relatively stress-free environment. The professor measures the menstrual cycle (in days) of each woman during the second month.The following data are obtained.

High stress 20 23 18 19 22

Relatively stress free 26 31 25 26 30

Assume you are evaluating H0 using the t test with = .052 tail. The correct conclusion is _________.

accept H0;stress does not affect the menstrual cycle

retain H0;we cannot conclude that stress affects the menstrual cycle

retain H0;stress affects the menstrual cycle

reject H0;stress affects the menstrual cycle