Chapter 10: Independent Samples

Question 1

What are two sample hypothesis tests used to make?

Answer 1

statistical decisions about relationships between two variables

Question 2

What comparisons can be made?

Answer 2

Two parameters to see whether they are equal

Question 3

What questions should you ask yourself?

Answer 3

Are they unequal enough to be statistically significant, Can we reject null that the two stats are equal and represent separate pops

Question 4

What can both z-tests and t-tests be used for comparing?

Answer 4

Means of interval and ratio level variables

Question 5

What are between groups comparisons?

Answer 5

determine if a difference between two groups is large enough to be statistically significant

Question 6

What is statistically significant?

Answer 6

Is difference large enough that we can reject null of no difference

Question 7

What determines the approach?

Answer 7

Size of samples, level of measurement, whether samples are IV or DV, whether variances of independent samples are equal, whether sd of pop is known or sd is used to estimate it

Question 8

What can z-tests be used to compare?

Answer 8

Proportions of nominal and ordinal variables

Question 9

What do independent samples have?

Answer 9

No overlap, mutually exclusive groups

Question 10

What do dependent samples have?

Answer 10

Some sort of overlap

Question 11

In regard to samples what could two data points have?

Answer 11

Two data points for same person, pairs of data points for two people who are matched

Question 12

What measurement of variables can be analyzed using t-tests?

Answer 12

Interval and ratio

Question 13

What is the main difference between independent samples and dependent samples?

Answer 13

Independent are mutually exclusive, dependent samples have some overlap or connection to each other

Question 14

What is the book definition of between-groups comparisons?

Answer 14

Data from independent samples

Question 15

What type of data do within-group comparisons use?

Answer 15

Dependent samples

Question 16

What is standard error?

Answer 16

Probability distribution is created for many values of means from many different samples

Question 17

What happens as the size of the samples increase?

Answer 17

Standard error becomes smaller

Question 17

What does the standard error becoming smaller indicate about the size of the sample?

Answer 17

Little variation around the population mean, smaller the standard error the more precise the estimate of the pop mean

Question 18

What happens if one or both sample has a sample less than n=30?

Answer 18

Use a t-test instead

Question 19

What does a t-test graph look like with smaller samples?

Answer 19

Relatively flat

Question 20

What does a t-test with a standard sample look like?

Answer 20

Very close to normal

Question 21

What happens with sample size and using a z-test or t-test to define which one?

Answer 21

Both samples must meet the same criterion for the test that is going to be used

Question 22

What happens if one variance is no more than twice the other?

Answer 22

They are considered approximately equal and a pooled estimate of the standard error can be used

Question 23

What is an explanation of the formula for pooled variance?

Answer 23

s21 and s22 are the sample variances (not standard deviations) and n1 and n2 are the sizes of the two samples (1 and 2). The square root is taken to complete the calculation as the estimate of the pooled standard deviation.

Question 24

What happens if the variances are not equal to each other?

Answer 24

Unpooled standard error is used

Question 25

Why can’t you use the pooled variance for unequal variances?

Answer 25

Because it can lead to unreliable results with the t-test

Question 26

What is “too different” defined as?”

Answer 26

One variance more than twice the other

Question 27

How to determine degrees of freedom from approximately equal variances?

Answer 27

determined by summing the sample sizes and then subtracting the number of samples

Question 28

What is the formula for approximately equal variances?

Answer 28

(n1 + n2) - 2

Question 29

What does the value for d tell us?

Answer 29

Mean difference between the two groups

Question 30

Can spooled by calculated using the sample size and standard deviations from the samples?

Answer 30

Yes

Question 31

Given the same t-statistic and same variances, a hypothesis test based on larger sample would likely show a smaller effect size?

Answer 31

No

Question 32

What are independent samples?

Answer 32

Selection of elements in one sample are not influenced by selection of elements in the other sample

Question 33

How to find df is the test has two samples?

Answer 33

Add the two degrees of freedom together

Question 34

What are the assumptions for independent sample t-tests?

Answer 34

Random sampling methods, sampling with replacement, normally shaped,