Ch.10 Stats

Using a two-tailed independent-measures t test, a researcher determines that the probability of the population mean difference falling between 1.23 and 4.22 is 95%. What alpha value did the researcher use?

0.05

For an independent-measures research study, the two sample means are found to be M1 = 15.5 and M2 = 17. If the pooled variance is 1.23, what would be the reported value of Cohen's d, and how would the effect size be described?

1.35 large effect D is always positive

A researcher reports an independent-measures t statistic with df = 30.If the two samples are the same size (n1 = n2), then how many individuals are in each sample?​

16

An independent-measures study uses two samples, each with n = 10, to compare two treatment conditions.What is the df value for the t statistic for this study?​

18

The results of an independent-measures research study are reported as "t(20) = 2.12, p < .05, two tails."For this study, what t values formed the boundaries for the critical region?​

2.086

An independent-measures study has one sample with n = 10 and a second sample with n = 15 to compare two experimental treatments.What is the df value for the t statistic for this study?​

23

What is the pooled variance for the following two samples?​ Sample 1:n = 8 and SS = 168 Sample 2:n = 6 and SS = 120

24

One sample from an independent-measures study has n = 16 with a variance of s2 = 65. The other sample has n = 25 and s2 = 70. What is the df value for the t statistic?

39

The data from an independent-measures research study produce a sample mean difference of 6 points and an estimated standard error of 2 points.If there are n = 8 scores in each sample, then the value for the t statistic is ____.​

6/2

Which set of sample characteristics is most likely to produce a significant value for the independent-measures t statistic?​

A large mean difference and small sample variances

An independent-measures design is also known as a _______________ design.

between-subjects design

Which of the following sets of data is least likely to reject the null hypothesis in a test with the independent-measures t statistic. Assume that other factors are held constant.

n = 15 and SS = 375 for both samples

Two samples are taken from separate populations. The sample and population mean from one group are M1 = 16 and μ1 = 14. The sample and population mean from the second groups are M2 = 21 and μ2 = 13. If the estimated standard error is S(M1 - M2) = 2, what is the t statistic?

-3

A sample of size n1 = 16 is taken from a group of bees in one hive, and the sample variance in weight is 1.2 grams. A sample of size n2 = 16 is taken from another hive, and the sample variance is 0.8 grams. What is the estimated standard error for the difference between the two means?

0.35

If all other factors are held constant, which of the following is true if the sample sizes and the sample variance increase in a one-tailed independent-measures t test?

Because the increase in sample sizes has little or no effect on effect size and the increase in sample variance causes a decrease in effect size, the combined effect will be a decrease in effect size.

How is an independent-measures design different from a study that makes inferences about the population mean from a sample mean?

In an independent-measures design, there are two independent samples that are compared to one another

A researcher obtains an independent-measures t statistic of t = 2.12 for a study comparing two treatments with a sample of n1 = 14 in one treatment and n2 = 10 in the other treatment. What is the correct decision for a regular one-tailed hypothesis test?

Reject the null hypothesis with α = .05 but not with α = .01.

A researcher obtains an independent-measures t statistic of t = 3.01 for a study comparing two treatments with a sample of n = 16 in each treatment. What is the correct decision for a regular two-tailed hypothesis test?

Reject the null hypothesis with α = .05 or with α = .01.

Which of the following would represent independent measures?

The average number of traffic tickets among men and women is measured to see if there is a statistically significant difference. Measuring whether age has an effect on the amount of time an individual can hold his breath under water. A sample of 10-year-olds is compared with a sample of 18-year-olds.

A research study measures the effect of age on the average driving speed by selecting a sample of teenage drivers and a sample of drivers between the ages of 20 and 25. Why is this an example of an independent-measures design?

There is one measure being taken for two non-overlapping samples.

In an independent measures test, a researcher is looking at the average height of Americans versus the average height of Australians. If μ1 and μ2 are the two population mean heights, what is the null hypothesis?

b. H0: μ1 − μ2 = 0

Why does a change in sample sizes have little or no effect on Cohen's d in an independent-measures t statistic?

c. Because the sample size occurs in the numerator as part of the difference in sample means and in the denominator as part of the pooled variance, and the effect of one is virtually cancelled out by the effect of the other.

One sample of n = 8 scores has a variance of s2 = 6 and a second sample of n = 8 scores has s2 = 10.If the pooled variance is computed for these two samples, then the value obtained will be ____.

exactly half way between 6 and 10

Which of the following will cause a researcher the most problems when trying the demonstrate statistical significance using a two-tailed independent-measures t test?

high variance

Which of the following is not an assumption for using the independent-measures t formula?

homogeneity of population means

For a research study measuring the effect of two treatments, the sample sizes are n 1 = 8 in one treatment and n 2 = 10 in the other treatment, and the pooled variance is 1.23. The sample means are M 1 = 21.2 and M 2 = 24.1, with corresponding population means of μ1 = 21.2 and μ2 = 23. Using a two-tailed t test, determine the t value for α = .05 and make a conclusion about the null hypothesis.

t = -2.09, therefore we do not reject the null hypothesis

Researchers conduct a hypothesis test and use the data from two separate sets of observations drawn from the same group of participants. Their research design is called a repeated-measures research design or a(n)____.

within-subjects

Two samples, each with n = 8, produce an independent-measures t statistic of t = -2.15.Which of the following decisions is justified for a two-tailed hypothesis test?​

​Fail to reject H0 with α = .05 and fail to reject with α = .01.