Question 1

When the variances are known, a test comparing two independent sample means would use the normal distribution.

Accepted Answer

A) True 
 B)False

Question 2

At Huge University, a sample of 200 business school seniors showed that 26 planned to pursue an MBA degree, compared with 120 of 800 arts and sciences seniors. We want to know if the proportion is higher in the arts and sciences group. For this test, the assumption of normality for the difference of proportions is:

Accepted Answer

A) clearly unjustified. 
B) clearly justified. 
C) a borderline call. 
A) clearly unjustified. 
B) clearly justified. 
C) a borderline call.

Question 3

A confidence interval for the difference of two population means:

Accepted Answer

A) must pool the sample variances. 
B) may or may not pool the sample variances. 
C) cannot be used to test for equal population means. 
A) must pool the sample variances. 
B) may or may not pool the sample variances. 
C) cannot be used to test for equal population means.

Question 4

Of 200 youthful gamers (under 18) who tried the new Z-Box-Plus game, 160 rated it "excellent," compared with only 144 of 200 adult gamers (18 or over). The test statistic to test the two proportions for equality would be:

Accepted Answer

A) 1.645 
B) 1.960 
C) 1.873 
D) 1.448 
A) 1.645 
B) 1.960 
C) 1.873 
D) 1.448

Question 5

A corporate analyst is testing whether mean inventory turnover has increased. Inventory turnover in six randomly chosen product distribution centers (PDCs) is shown. $\begin{array} {  |l | c | c | } 
\hline & { \text { This Year } } & \text { Last Year } \
\hline  \text { PDC 1 } & 5.1 & 4.1 \
\hline  \text { PDC 2 } & 3.9 & 2.9 \
\hline  \text { PDC 3 } & 4.8 & 2.8 \
\hline \text { PDC 4 } & 3.4 & 3.4 \
\hline  \text { PDC 5 } & 4.6 & 2.6 \
\hline  \text { PDC 6 } & 7.7 & 4.7 \
\hline
\end{array}$ The right-tailed critical value at ? = 0.005 is:

Accepted Answer

A) 1.645 
B) 1.479 
C) 4.032 
D) 2.015 
A) 1.645 
B) 1.479 
C) 4.032 
D) 2.015

Question 6

The coach of an adult Master's Swim class selected eight swimmers within each of the two age groups shown below. A 50-yard freestyle time is recorded for each swimmer. The resulting times (seconds) are shown below. Which statistical test would you choose to compare the two groups? $$\begin{array} { c c c } 
&  { \text { Age Group } } \
\text { Obs } & 25 - 34 \text { Yrs } & 35 - 44 \text { Yrs } \
1 & 26.26 & 31.08 \
2 & 28.44 & 28.63 \
3 & 26.61 & 25.65 \
4 & 29.74 & 31.81 \
5 & 26.94 & 27.22 \
6 & 26.31 & 30.56 \
7 & 34.68 & 33.38 \
8 & 22.55 & 30.82 \
& & \
\text { Mean } & 27.69 & 29.89 \
\text { St Dev } & 3.50 & 2.54
\end{array}$$

Accepted Answer

A) t-test for independent samples with known variances 
B) t-test for independent samples with unknown variances 
C) t-test for paired samples 
D) z-test for two independent proportions 
A) t-test for independent samples with known variances 
B) t-test for independent samples with unknown variances 
C) t-test for paired samples 
D) z-test for two independent proportions

Question 7

A medical researcher wondered if there is a significant difference between the mean birth weight of boy and girl babies. A random sample of babies' weights (pounds) showed the following. $$\begin{array} { l l l l l l } 
\text { Boys } & 8.0 & 4.7 & 7.3 & 6.2 & 3.4 \
\text { Girls } & 5.3 & 2.8 & 6.4 & 6.8 & 7.4
\end{array}$$ How many degrees of freedom would be used to test for a zero difference in means?

Accepted Answer

A) 4 
B) 8 
C) 10 
D) Must know ? to say. 
A) 4 
B) 8 
C) 10 
D) Must know ? to say.

Question 8

Based on a random sample of 13 tire changes, the mean time to change a tire on a Boeing 777 has a mean of 59.5 minutes with a standard deviation of 8.4 minutes. For 10 tire changes on a Boeing 787, the mean time was 64.3 minutes with a standard deviation of 12.4 minutes. To test for equal variances in a two-tailed test at α = .10, the critical values are:

Accepted Answer

A) 3.73 and 0.228 
B) 2.51 and 3.67 
C) 3.07 and 0.398 
D) 3.07 and 0.357 
A) 3.73 and 0.228 
B) 2.51 and 3.67 
C) 3.07 and 0.398 
D) 3.07 and 0.357

Question 9

Litter sizes (number of pups) for randomly chosen dogs from two breeds were compared. The sample data were entered into Excel, and the following results were produced. $$\begin{array}{l}
\text { t-Test: Two-Sample Assuming Unequal Variances }\
\begin{array} { l r r } 
\hline & \text { Dalmation } & \text { Labrador } \
\hline \text { Mean } & 4.8125 & 5.461538 \
\text { Variance } & 3.4958333 & 0.602564 \
\text { Observations } & 16 & 13 \
\text { Hypothesized Mean Diff } & 0 & \
\text { df } & 21 & \
\text { t Stat } & - 1.261183 & \
\hline
\end{array}
\end{array}$$ What is the p-value for a left-tailed test comparing the means at ? = .05?

Accepted Answer

A) Less than .10 
B) More than .10 
C) Between .10 and .05 
D) Between .05 and .01 
A) Less than .10 
B) More than .10 
C) Between .10 and .05 
D) Between .05 and .01

Question 10

Which is not true of the two-tailed F-test for equality of variances?

Accepted Answer

A) It requires reversing the numerator and denominator d.f. to obtain the left-tail critical value. 
B) It can be avoided by "folding" the larger variance into the numerator and adjusting α. 
C) It is fairly robust to the presence of nonnormality in the populations being sampled. 
A) It requires reversing the numerator and denominator d.f. to obtain the left-tail critical value. 
B) It can be avoided by "folding" the larger variance into the numerator and adjusting α. 
C) It is fairly robust to the presence of nonnormality in the populations being sampled.

Question 11

Of 200 youthful gamers (under 18) who tried the new Z-Box-Plus game, 160 rated it "excellent," compared with only 144 of 200 adult gamers (18 or over). The p-value for a right-tailed test to compare the two proportions would be approximately:

Accepted Answer

A) .042 
B) .031 
C) .054 
D) .095 
A) .042 
B) .031 
C) .054 
D) .095

Question 12

If the population variances are exactly equal, the sample F test statistic will be zero.

Accepted Answer

A) True 
 B)False

Question 13

Jason wants to perform a two-tailed test for equality between two independent sample proportions. Each sample has at least 10 "successes" and 10 "failures." Jason's test statistic is -1.44. What is his p-value?

Accepted Answer

A) .1498 
B) .0749 
C) .9251 
D) Between .01 and .05 
A) .1498 
B) .0749 
C) .9251 
D) Between .01 and .05

When the variances are known, a test comparing two independent sample means would use the normal distribution.

A confidence interval for the difference of two population means:

Of 200 youthful gamers (under 18) who tried the new Z-Box-Plus game, 160 rated it "excellent," compared with only 144 of 200 adult gamers (18 or over). The test statistic to test the two proportions for equality would be:

Which is not true of the two-tailed F-test for equality of variances?

Of 200 youthful gamers (under 18) who tried the new Z-Box-Plus game, 160 rated it "excellent," compared with only 144 of 200 adult gamers (18 or over). The p-value for a right-tailed test to compare the two proportions would be approximately:

If the population variances are exactly equal, the sample F test statistic will be zero.

Jason wants to perform a two-tailed test for equality between two independent sample proportions. Each sample has at least 10 "successes" and 10 "failures." Jason's test statistic is -1.44. What is his p-value?

Overview of Statistics

Data Collection

Describing Data Visually

Descriptive Statistics

Probability

Discrete Probability Distributions

Continuous Probability Distributions

Sampling Distributions and Estimation

One-Sample Hypothesis Tests

Analysis of Variance

Simple Regression

Multiple Regression

Time Series Analysis

Chi-Square Tests

Nonparametric Tests

Quality Management

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Exam 10: Two-Sample Hypothesis Tests

When the variances are known, a test comparing two independent sample means would use the normal distribution.

A confidence interval for the difference of two population means:

Of 200 youthful gamers (under 18) who tried the new Z-Box-Plus game, 160 rated it "excellent," compared with only 144 of 200 adult gamers (18 or over). The test statistic to test the two proportions for equality would be:

Which is not true of the two-tailed F-test for equality of variances?

Of 200 youthful gamers (under 18) who tried the new Z-Box-Plus game, 160 rated it "excellent," compared with only 144 of 200 adult gamers (18 or over). The p-value for a right-tailed test to compare the two proportions would be approximately:

If the population variances are exactly equal, the sample F test statistic will be zero.

Jason wants to perform a two-tailed test for equality between two independent sample proportions. Each sample has at least 10 "successes" and 10 "failures." Jason's test statistic is -1.44. What is his p-value?

Overview of Statistics

Data Collection

Describing Data Visually

Descriptive Statistics

Probability

Discrete Probability Distributions

Continuous Probability Distributions

Sampling Distributions and Estimation

One-Sample Hypothesis Tests

Analysis of Variance

Simple Regression

Multiple Regression

Time Series Analysis

Chi-Square Tests

Nonparametric Tests

Quality Management

Filters