Chp 9 stats

What are the degrees of freedom for an independent-samples t-test using one sample with n = 13 and one sample with n = 15?

26

Suppose a researcher assessed attitudes towards a certain brand of soda before and after conducting a taste test and noted the following results:

-2

By convention, the mean of the sampling distribution equals

0

When Ho is true, what does the mean of the sampling distribution of differences between means equal?

0

How many subjects participated in an independent-samples t-test if a researcher reports t(20) = 3.68?

22

b.

Which of the following is the appropriate statistic for describing the effect size in a two-sample experiment?

Suppose you perform a two-tailed independent-samples t-test, using α = 0.05, with 15 participants in one group and 16 participants in the other group. Your tobt is 4.56, which is significant. What is the correct way to report this

t(29) = 4.56; p < 0.05

To determine the extent to which the conditions of the independent variable determine dependent scores, we should compute

the effect size.

In order to find the t-obtained for an independent t-test, which step is not required?

Set up the sampling distribution

What can we conclude if we reject the null hypothesis in an independent-samples t-test?

The difference between our sample means is unlikely to be representing zero difference in the population means.

What does the homogeneity of variance assumption state?

The variance in one population is equal to the variance in the other population

If a researcher predicts the experimental treatment X2 will produce an increase in an independent-samples t-test

Ho:mew1-mew2>0

How is the proportion of variance accounted for calculated?

it is the squared point-biserial correlation coefficient.

In a study to determine the effectiveness of pain management therapy in persons with chronic pain, 20 individuals experiencing chronic pain were randomly selected. Ten of these individuals were assigned to receive pain management therapy and the other 10 to receive no therapy. Descriptive statistics for each group are provided below.

a. An independent samples t-test. b. df = (10 - 1) + (10 - 1) = 18 c. = 2.101 d. e. t(18)=2.45, p < .05 so reject null hypothesis f. 62-53 ------------------=1.77 squer root 67.525

Renee is studying the effect of positive reinforcement for her psychology class. She assigns 16 pigeons to two different positive reinforcement schedules. After training the pigeons, she measures the number of correct responses by each in 10 trials. Using a two-tailed test and α = .05, use the data below to determine whether or not there is a difference between the two schedules.

b. df = (8 - 1) + (8 - 1) = 14 c. = 2.145 d. = 6.375; = 5.375 e. 0.776 f. tbot=1.29 t(14)=1.29, p > .05 Fail to reject the null hypothesis It is not appropriate to calculate effect size.

Renee is studying the effect of positive reinforcement for her psychology class. She gets 16 pigeons. These pigeons are from eight egg clutches with two pigeons from each clutch. Renee matches each pigeon in Reinforcement Schedule A with its clutchmate in Reinforcement Schedule B. After training the pigeons, she measures the number of correct responses by each in 10 trials. Using a two-tailed test and alpa=0.5, use the data below to determine whether or not there is a difference between the two schedules.

b. df = 8 - 1 = 7 c. = 2.365 d. = 2.16 e. . Fail to reject the null hypothesis.

An appropriate example of a repeated measures design would be

comparing individual attitudes about drinking before and after viewing a film on the topic.

The sampling distribution of differences between means is the distribution of all possible

differences between two means when drawn from the raw score populations described by .

In an experiment, the "proportion of variance accounted for" is also called the

effect size.

If the variance for Sample 1 is 5 and the variance for Sample 2 is 3, where n1= 10 and n2 = 12, what is sx1-x2 ?

0.85

If = 20, = 220, and N = 10, what is sD?

1.41

For a study with a related samples design and 30 participants in which each participant is measured twice (repeated measures), what is the critical value? Assume a two-tailed test with α = .05.

2.045

What are the degrees of freedom for an independent-samples t-test using two samples with n = 20 in each sample?

18

If singmaD= 20, N = 10, and = 4, what is tobt when Ho:mewD=0 and Ha: mewD not equal 0 ?

3.16

independent-samples t-test.

At a card players' club, the poker players had a contest with the blackjack players to see who could win the most money. The appropriate design for testing the significance of the difference between the means is

related-samples t-test.

Eighteen overweight volunteers weighed themselves before and after a two-week diet. The appropriate design for testing the significance of the difference between the means is

If a researcher predicts the experimental treatment will produce an increase in an independent-samples t-test , how will the alternative hypothesis be stated?

Ha: mew1-mew2<0

If a researcher predicts the experimental treatment X2 will produce an decrease in an independent-samples t-test , how will the alternative hypothesis be stated?

Ha:mew1-mew2>0

If a researcher predicts the experimental treatment X2 will produce a decrease in an independent-samples t-test , how will the null hypothesis be stated?

Ho:mew1-mew2<0

State the null hypothesis for a two-tailed independent samples experiment.

Ho:mew1-mew2=0

related-samples t-test.

In a study involving stress among college students, a group of seniors are asked to complete a stress survey. After a two-hour seminar on relaxation methods, they are asked to complete the stress survey again. The appropriate design for testing the significance of the difference between the means is

What does the independent-samples t-test determine?

It determines the probability of obtaining the observed difference between X1 and X2 when Ho is true.

independent-samples t-test.

The first 10 students who arrived for the Friday lecture filled out a questionnaire on their attitudes toward the instructor. The first 10 who were late for the lecture were spotted, and afterward filled out the same questionnaire. The appropriate design for testing the significance of the difference between the means is

independent-samples t-test.

The freshmen competed with the sophomores to see who could raise the most money by recycling. The appropriate design for testing the significance of the difference between the means is

What are we stating if we reject the null hypothesis for the independent-samples t-test?

The sample mean difference represents no difference between two population μs.

Which of the following is not one of the assumptions of the t-test for independent samples?

The standard deviation of at least one of the populations is known.

What is the standard error of the difference?

The standard deviation of the sampling distribution of differences between means

What is pooled variance?

The weighted average of the sample variances

How is the null hypothesis of the independent-samples t-test verbalized?

There is no difference between the means for the two conditions of the independent variable.

Suppose you measure the IQ of 14 subjects with short index fingers and the IQ of 14 subjects with long index fingers. You compute an independent-samples t-test, and the is 0.29, which is not statistically significant. What is the most appropriate conclusion?

We do not have convincing evidence our results are due to anything other than sampling error.

Suppose the average reading speed of 15 randomly selected elementary school students is 25, and the average reading speed of 15 randomly selected middle school students is 31. You compute an independent-samples t-test, and your tobt is 5.72, which is statistically significant. What is the most appropriate conclusion?

We have evidence older students tend to read faster.

In a study to determine the effectiveness of pain management therapy in persons with chronic pain, 12 individuals experiencing chronic pain were selected. Based on each individual's assessment of his or her pain level, each participant in the group receiving the therapy was matched with a participant in the group who did not receive the therapy. Descriptive statistics regarding the differences in scores are provided below. sigmaD= 13 sigmaD^2=55 and N=6

a. A related-samples t-test b. df = (6 - 1) = 5 c. = 2.571 d. = 5.37 e. = 0.946 f. t(5) = 2.291, p > 0.05 Fail to reject the null hypothesis It is not appropriate to calculate the effect size.

Julius has conducted a very small study of the amount of sleep his dorm mates get each night. He believes those who are on one of the school's sports teams will get more sleep than those who are not. Julius surveyed 12 people. Of these, 6 played on a sports team, and 6 did not. The descriptive statistics from his survey are given below. Use = .05 and a one-tailed test in the upper tail.

a. Independent samples t-test b. df = (6 - 1) + (6 - 1) = 10 c. = +1.812 d. = 1.75 t(10) = 1.75, p > .05. Fail to reject the null hypothesis. It is not appropriate to calculate the effect size.

Julius has conducted a very small study of the amount of sleep his dorm mates get each night. He believes those who are on one of the school's sports teams will get more sleep than those who are not. Julius asked 6 people in his dorm who do not play sports and 6 who do play sports to participate. Because he thinks the number of credit hours a student is taking also might impact sleep habits, he matched each person in the "plays sports" group with a person in the "does not play sports" group who was carrying the same number of hours. The descriptive statistics from his survey are given below. Conduct an appropriate one-tailed t-test in the upper tail using α = .05.

a. Related-samples t-test b. df = 6 - 1 = 5 c. = +2.015 d. = 2.28 e. t(5) = 2.28, p < .05 Reject the null hypothesis 1.367 f. -------------------=0.0930 1.469

A Cohen's d value of .5 would be viewed as indicative of a effect.

medium

The freshmen competed with the sophomores to see who could raise the most money by recycling. Each freshman was paired with a sophomore of the same gender.The appropriate design for testing the significance of the difference between the means is

related-samples t-test.

Suppose a researcher compares 50 pairs of husbands and wives on a variety of attitudes. In doing so, the researcher is making use of _________________ samples with a ______________________ design.

related; matched-samples

Suppose you tested two age groups on the number of details they could recall from a paragraph. The mean for the older group is 16, and the mean for the younger group is 14. Further suppose you fail to reject the null hypothesis for this independent-samples t-test. What best accounts for the difference between these sample means?

sampling error

N represents _____, whereas n represents _____.

the total number of scores in the study; the number of scores in each sample