PSYC 240 Unit 2

A researcher conducts a hypothesis test using a sample of n=20 from an unknown population. What is the df value for the t statistic? a. 19 b. 20 c. 21 d. Cannot be determined from the information given

a. 19

For the following data from a repeated-measures study: a. Find the difference scores b. Calculate M(D) and the variance for the difference scores c. Calculate the estimated standard error for the mean difference d. Determine the t-statistics. e. What conclusion is appropriate? f. Calculate Cohen's d. g. What type of error could you make given these results? ---Subject - Treatment 1 - Treatment 2 ---A - 12 - 14 ---B - 6 - 16 ---C - 8 - 10 ---D - 9 - 11

a. 2, 10, 2, 2 b. M(D)=4, s(2)=16 c. SE-2 d. t=2 e. Fail to reject H(o) f. d=1 g. Type II error

Two samples, each with n=5 scores, have a pooled variance of 40. What is the estimated standard error for the sample mean difference? a. 4 b. 8 c. 10 d. 20

a. 4

Which set of characteristics will produce the smallest value for the estimated standard error? a. A large sample size and a small sample variance b. A large sample size and a large sample variance c. A small sample size and a small sample variance d. A small sample size and a large sample variance

a. A large sample size and a small sample variance

Which of the following describes what a confidence interval does? a. It uses a sample mean to estimate the corresponding population mean. b. It uses a population mean to predict a sample mean. c. It uses a level of confidence to estimate a sample mean. d. It uses the sample mean to determine a level of confidence.

a. It uses a sample mean to estimate the corresponding population mean.

Which of the following accurately describes the critical region? a. Outcomes with a very low probability if the null hypothesis is true b. Outcomes with a high probability if the null hypothesis is true c. Outcomes with a very low probability whether or not the null hypothesis is true d. Outcomes with a high probability whether or not the null hypothesis is true

a. Outcomes with a very low probability if the null hypothesis is true

A hypothesis test involves a comparison of which two elements? a. Research results from a sample and a hypothesis about a population b. Research results from a population and a hypothesis about a sample c. Research results from a population and a hypothesis about the population d. Research results from a sample and a hypothesis about the sample

a. Research results from a sample and a hypothesis about a population

A researcher conducts an independent-measures study examining the effectiveness of a group exercise program at an assisted living facility for elderly adults. One group of residents is selected to participate in the program, and a second group serves as a control. After 6 weeks, the researcher records a combined score measuring balance and strength for each individual. The data are as follows: Control: n=10, M=12, SS=120.5 Exercise: n=15, M=15.5, SS=190.0 a. Does the exercise program have a significant effect? Use an alpha level of .05, two tails. b. Compute Cohen's d to measure the size of the treatment effect.

a. Sp(2)=13.5, t=2.33, regret H(o) b. d=.95

Which of the following is the correct null hypothesis for an independent-measures t test? a. μ(1)-μ(2)=0 b. M(1)-M(2)=0 c. μ(1)-μ(2) 0 d. M(1)-M(2) 0

a. μ(1)-μ(2)=0

A researcher would like to determine whether an over-the-counter cold medication has an effect on mental alertness. A sample of n=16 participants is obtained, and each person is given a standard dose of the medication one hour before being tested in a driving simulation task. For the general individuals in the sample had an average score of M=56.5. a. Can the researcher conclude that scores on the driving simulation task are significantly different after taking the medication? Use a two-tailed test with a α=.05. b. Compute Cohen's d to measure the size of the effect.

a. σM=2, z=-1.75 b. d=.44

An independent-measures study comparing two treatment conditions produces a t statistic with df=18. If the two samples are the same size, how many participants were in each of the samples? a. 9 b. 10 c. 19 d. 20

b. 10

If an independent-measures design is being used to compare two treatment conditions, then how many different groups of participants would be needed and how many scores would there be for each participant? a. 1 group, 1 score each b. 2 groups, 1 score each c. 1 group, 2 scores each d. 2 groups, 2 scores each

b. 2 groups, 1 score each

An independent-measures research study with n=5 participants in each treatment produces sample variance of 8 and 10, and a 2-point difference between the two treatment means. Given this information, what is the value of Cohen's d? a. 2/2 b. 2/3 c. 2/9 d. 2/18

b. 2/3

For a population with μ=80 and σ=20, the distribution of sample means based on n=16 will have an expected value of _______ and a standard error of _______. a. 5;80 b.80;5 c. 20;20 d. 80;1.25

b. 80;5

A researcher plans to conduct a research study comparing two treatment conditions with a total of 20 participants. Which of the following designs would produce 20 scores in each treatment? a. An independent-measure design b. A repeated-measures design c. A matched-subjects design d. All of the other options would produce 20 scores in each treatment.

b. A repeated-measures design

One sample has n=10 scores and a variance of s(2)=20, and a second sample has n=15 scores and a variance of s(2)=30. What can you conclude about the pooled variance for these two samples? a. It will be closer to 20 than to 30. b. It will be closer to 30 than to 20. c. It will be exactly halfway between 20 and 30. d. Cannot be determined without more information

b. It will be closer to 30 than to 20.

Which of the following is an accurate definition of a Type I error? a. Rejecting a false null hypothesis b. Rejecting a true null hypothesis c. Failing to reject a false null hypothesis d. Failing to reject a true null hypothesis

b. Rejecting a true null hypothesis

Which of the following is a fundamental difference between the t statistic and a z-score? a. The t statistic uses the sample mean in place of the population mean. b. The t statistic uses the sample variance in place of the population variance. c. The t statistic computes the standard error by dividing the standard deviation by n-1 instead of dividing by n d. All of the above are differences between t and z

b. The t statistic uses the sample variance in place of the population variance.

Which of the following is not needed to compute a t statistic? a. A hypothesized value for the population mean b. The value of the population variance or standard deviation c. The value of the sample mean d. The value of the sample variance or standard deviation

b. The value of the population variance or standard deviation

Two separate samples are being used to estimate the population mean difference between two treatment conditions. Which of the following would produce the widest confidence interval? a. n(1)=n(2)=10 with a pooled variance of 10 b. n(1)=n(2)=10 with a pooled variance of 100 c. n(1)=n(2)=20 with a pooled variance of 10 d. n(1)=n(2)=20 with a pooled variance of 100

b. n(1)=n(2)=10 with a pooled variance of 100

The results of an independent-measures research study are reported as "t(22)=2.12, p<.05, two tails." For this study, what t values formed the boundaries for the critical region? a. ±2.080 b. ±2.074 c. ±2.069 d. ±2.064

b. ±2.074

Which of the following is the correct null hypothesis for a repeated-measures t test? a. M(D)=0 b. μ(D)=0 c. μ(1)=μ(2) d. M(1)=M(2)

b. μ(D)=0

A sample of n=100 scores is selected from a population with μ=80 and σ=20. On average, how much error is expected between the sample mean and the population mean? a. 0.2 points b. 0.8 points c. 2 points d. 4 points

c. 2 points

Using an independent-measures t, the 90% confidence interval for the difference between two treatment conditions. Which of the following would produce the widest confidence interval for the difference between two population means ranges from 19-23. Based on this confidence interval, how big is the difference between the two sample means> a. 4 points b. 19 points c. 21 points d. 23 points

c. 21 points

An independent-measures study uses n=15 participants in each group to compare two treatment conditions. What is the df value for the t statistic for this study? a. 14 b. 15 c. 28 d. 29

c. 28

Which combination of factors would definitely increase the width of a confidence interval? a. Increase the sample mean and increase the size of the sample b. Decrease the sample mean and increase the size of the sample c. Increase the sample mean and increase the percentage of confidence d. Decrease the sample mean and decrease the percentage

c. Increase the sample mean and increase the percentage of confidence

Which of the following will not increase the width of a confidence interval? a. Increase the percentage of confidence from 80% to 90% b. Reduce the sample size from n=25 to n=16 c. Increase the sample mean from M(D)=2 to M(D)=4 d. All of the other options will increase the width of a confidence interval

c. Increase the sample mean from M(D)=2 to M(D)=4

If a hypothesis test produces a z-score in the critical region, what decision should be made? a. Reject the alternative hypothesis b. Fail to reject the alternative hypothesis c. Reject the null hypothesis d. Fail to reject the null hypothesis

c. Reject the null hypothesis

A repeated-measures study and an independent-measures study both produced a t statistic with df=10. How many individuals participated in each study? a. 12 for repeated-measures and 11 for independent-measures b. 12 for repeated-measures and 12 for independent-measures c. 11 for repeated-measures and 11 for independent-measures d. 11 for repeated-measures and 12 for independent-measures

d. 11 for repeated-measures and 12 for independent-measures

What is the pooled variance for the following two samples? Sample 1: n=8 and SS=168 Sample 2: n=6 and SS=120 a. 7 b. square root of 7 c. 20.57 d. 24

d. 24

What is the standard error of M? a. It is the sample mean. b. It is the sample standard deviation. c. It is the mean of the distribution of sample means. d. It is the standard deviation of the distribution of sample means.

d. It is the standard deviation of the distribution of sample means

If the sample size is held constant, which of the following will produce the widest 90% confidence interval for the population mean difference for a repeated-measures study? a. M(D)=5 with s(2)=5 for the difference scores b. M(D)=5 with s(@)=10 for the difference scores c. M(D)=3 with s(2)=10 for the difference scores d. M(D)=3 with s(2)=20 for the difference scores

d. M(D)=3 with s(2)=20 for the difference scores

A sample is selected from a population with μ=50. After a treatment is administered to the individuals in the sample, the mean is found to be M=55 and the variance is s(2)=64. If the sample has n=16 scores, the conduct a hypothesis test to evaluate the significance of the treatment effect and calculate Cohen's d to measure the size of the treatment effect. Use a two-tailed test with α=.05

t= 2.50 d=.625

A sample of n=16 scores has a mean of M=58 with SS=960. Use the sample to construct the 90% confidence interval for μ.

μ=58±1.753(2)