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Inside Collection (Textbook):

Textbook by: Barbara Illowsky, Ph.D., Susan Dean. E-mail the authors

# Homework

For questions Exercise 1 - Exercise 10, indicate which of the following choices best identifies the hypothesis test.

• A. Independent group means, population standard deviations and/or variances known
• B. Independent group means, population standard deviations and/or variances unknown
• C. Matched or paired samples
• D. Single mean
• E. 2 proportions
• F. Single proportion

## Exercise 1

A powder diet is tested on 49 people and a liquid diet is tested on 36 different people. The population standard deviations are 2 pounds and 3 pounds, respectively. Of interest is whether the liquid diet yields a higher mean weight loss than the powder diet.

A

## Exercise 2

A new chocolate bar is taste-tested on consumers. Of interest is whether the proportion of children that like the new chocolate bar is greater than the proportion of adults that like it.

## Exercise 3

The mean number of English courses taken in a two–year time period by male and female college students is believed to be about the same. An experiment is conducted and data are collected from 9 males and 16 females.

B

## Exercise 4

A football league reported that the mean number of touchdowns per game was 5. A study is done to determine if the mean number of touchdowns has decreased.

## Exercise 5

A study is done to determine if students in the California state university system take longer to graduate than students enrolled in private universities. 100 students from both the California state university system and private universities are surveyed. From years of research, it is known that the population standard deviations are 1.5811 years and 1 year, respectively.

A

## Exercise 6

According to a YWCA Rape Crisis Center newsletter, 75% of rape victims know their attackers. A study is done to verify this.

## Exercise 7

According to a recent study, U.S. companies have an mean maternity-leave of six weeks.

D

## Exercise 8

A recent drug survey showed an increase in use of drugs and alcohol among local high school students as compared to the national percent. Suppose that a survey of 100 local youths and 100 national youths is conducted to see if the proportion of drug and alcohol use is higher locally than nationally.

## Exercise 9

A new SAT study course is tested on 12 individuals. Pre-course and post-course scores are recorded. Of interest is the mean increase in SAT scores.

C

## Exercise 10

University of Michigan researchers reported in the Journal of the National Cancer Institute that quitting smoking is especially beneficial for those under age 49. In this American Cancer Society study, the risk (probability) of dying of lung cancer was about the same as for those who had never smoked.

### Directions:

For each of the word problems, use a solution sheet to do the hypothesis test. The solution sheet is found in 14. Appendix (online book version: the link is "Solution Sheets"; PDF book version: look under 14.5 Solution Sheets). Please feel free to make copies of the solution sheets. For the online version of the book, it is suggested that you copy the .doc or the .pdf files.

### Note:

If you are using a student's-t distribution for a homework problem below, including for paired data, you may assume that the underlying population is normally distributed. (In general, you must first prove that assumption, though.)

### Exercise 11

A powder diet is tested on 49 people and a liquid diet is tested on 36 different people. Of interest is whether the liquid diet yields a higher mean weight loss than the powder diet. The powder diet group had an mean weight loss of 42 pounds with a standard deviation of 12 pounds. The liquid diet group had an mean weight loss of 45 pounds with a standard deviation of 14 pounds.

#### Solution

• d. t 68 . 44 t 68 . 44 size 12{t rSub { size 8{"68" "." "44"} } } {}
• e. -1.04
• f. 0.1519
• h. Decision: Do not reject null

### Exercise 12

The mean number of English courses taken in a two–year time period by male and female college students is believed to be about the same. An experiment is conducted and data are collected from 29 males and 16 females. The males took an average of 3 English courses with a standard deviation of 0.8. The females took an average of 4 English courses with a standard deviation of 1.0. Are the means statistically the same?

### Exercise 13

A study is done to determine if students in the California state university system take longer to graduate, on average, than students enrolled in private universities. 100 students from both the California state university system and private universities are surveyed. Suppose that from years of research, it is known that the population standard deviations are 1.5811 years and 1 year, respectively. The following data are collected. The California state university system students took on average 4.5 years with a standard deviation of 0.8. The private university students took on average 4.1 years with a standard deviation of 0.3.

#### Solution

Standard Normal

• e. z = 2 . 14 z = 2 . 14 size 12{z=2 "." "14"} {}
• f. 0.0163
• h. Decision: Reject null when α = 0 . 05 α = 0 . 05 size 12{a=0 "." "05"} {} ; Do not reject null when α = 0 . 01 α = 0 . 01 size 12{a=0 "." "05"} {}

### Exercise 14

A new SAT study course is tested on 12 individuals. Pre-course and post-course scores are recorded. Of interest is the mean increase in SAT scores. The following data are collected:

 Pre-course score Post-course score 1200 1300 960 920 1010 1100 840 880 1100 1070 1250 1320 860 860 1330 1370 790 770 990 1040 1110 1200 740 850

### Exercise 15

A recent drug survey showed an increase in use of drugs and alcohol among local high school seniors as compared to the national percent. Suppose that a survey of 100 local seniors and 100 national seniors is conducted to see if the proportion of drug and alcohol use is higher locally than nationally. Locally, 65 seniors reported using drugs or alcohol within the past month, while 60 national seniors reported using them.

#### Solution

• e. 0.73
• f. 0.2326
• h. Decision: Do not reject null

### Exercise 16

A student at a four-year college claims that mean enrollment at four–year colleges is higher than at two–year colleges in the United States. Two surveys are conducted. Of the 35 two–year colleges surveyed, the mean enrollment was 5068 with a standard deviation of 4777. Of the 35 four-year colleges surveyed, the mean enrollment was 5466 with a standard deviation of 8191. (Source: Microsoft Bookshelf)

### Exercise 17

A study was conducted by the U.S. Army to see if applying antiperspirant to soldiers’ feet for a few days before a major hike would help cut down on the number of blisters soldiers had on their feet. In the experiment, for three nights before they went on a 13-mile hike, a group of 328 West Point cadets put an alcohol-based antiperspirant on their feet. A “control group” of 339 soldiers put on a similar, but inactive, preparation on their feet. On the day of the hike, the temperature reached 83° F. At the end of the hike, 21% of the soldiers who had used the antiperspirant and 48% of the control group had developed foot blisters. Conduct a hypothesis test to see if the proportion of soldiers using the antiperspirant was significantly lower than the control group. (Source: U.S. Army study reported in Journal of the American Academy of Dermatologists)

#### Solution

• e. -7.33
• f. 0
• h. Decision: Reject null

### Exercise 18

We are interested in whether the proportions of female suicide victims for ages 15 to 24 are the same for the white and the black races in the United States. We randomly pick one year, 1992, to compare the races. The number of suicides estimated in the United States in 1992 for white females is 4930. 580 were aged 15 to 24. The estimate for black females is 330. 40 were aged 15 to 24. We will let female suicide victims be our population. (Source: the National Center for Health Statistics, U.S. Dept. of Health and Human Services)

### Exercise 19

At Rachel’s 11th birthday party, 8 girls were timed to see how long (in seconds) they could hold their breath in a relaxed position. After a two-minute rest, they timed themselves while jumping. The girls thought that the mean difference between their jumping and relaxed times would be 0. Test their hypothesis.

 Relaxed time (seconds) Jumping time (seconds) 26 21 47 40 30 28 22 21 23 25 45 43 37 35 29 32

#### Solution

• d. t 7 t 7 size 12{t rSub { size 8{7} } } {}
• e. -1.51
• f. 0.1755
• h. Decision: Do not reject null

### Exercise 20

Elizabeth Mjelde, an art history professor, was interested in whether the value from the Golden Ratio formula, larger+smaller dimensionlarger dimensionlarger+smaller dimensionlarger dimension size 12{ left ( { {l"arg"e+ ital "small"} over {l"arg"e} } right )} {}was the same in the Whitney Exhibit for works from 1900 – 1919 as for works from 1920 – 1942. 37 early works were sampled. They averaged 1.74 with a standard deviation of 0.11. 65 of the later works were sampled. They averaged 1.746 with a standard deviation of 0.1064. Do you think that there is a significant difference in the Golden Ratio calculation? (Source: data from Whitney Exhibit on loan to San Jose Museum of Art)

### Exercise 21

One of the questions in a study of marital satisfaction of dual–career couples was to rate the statement, “I’m pleased with the way we divide the responsibilities for childcare.” The ratings went from 1 (strongly agree) to 5 (strongly disagree). Below are ten of the paired responses for husbands and wives. Conduct a hypothesis test to see if the mean difference in the husband’s versus the wife’s satisfaction level is negative (meaning that, within the partnership, the husband is happier than the wife).

 Wife’s score 2 2 3 3 4 2 1 1 2 4 Husband’s score 2 2 1 3 2 1 1 1 2 4

#### Solution

• d. t 9 t 9 size 12{t rSub { size 8{9} } } {}
• e. t = 1 . 86 t = 1 . 86 size 12{t= - 1 "." "86"} {}
• f. 0.0479
• h. Decision: Reject null, but run another test

### Exercise 22

Ten individuals went on a low–fat diet for 12 weeks to lower their cholesterol. Evaluate the data below. Do you think that their cholesterol levels were significantly lowered?

 Starting cholesterol level Ending cholesterol level 140 140 220 230 110 120 240 220 200 190 180 150 190 200 360 300 280 300 260 240

### Exercise 23

Mean entry level salaries for college graduates with mechanical engineering degrees and electrical engineering degrees are believed to be approximately the same. (Source: http:// www.graduatingengineer.com). A recruiting office thinks that the mean mechanical engineering salary is actually lower than the mean electrical engineering salary. The recruiting office randomly surveys 50 entry level mechanical engineers and 60 entry level electrical engineers. Their mean salaries were $46,100 and$46,700, respectively. Their standard deviations were $3450 and$4210, respectively. Conduct a hypothesis test to determine if you agree that the mean entry level mechanical engineering salary is lower than the mean entry level electrical engineering salary.

#### Solution

• d. t 108 t 108 size 12{t rSub { size 8{"108"} } } {}
• e. t = 0 . 82 t = 0 . 82 size 12{t= - 0 "." "82"} {}
• f. 0.2066
• h. Decision: Do not reject null

### Exercise 24

A recent year was randomly picked from 1985 to the present. In that year, there were 2051 Hispanic students at Cabrillo College out of a total of 12,328 students. At Lake Tahoe College, there were 321 Hispanic students out of a total of 2441 students. In general, do you think that the percent of Hispanic students at the two colleges is basically the same or different? (Source: Chancellor’s Office, California Community Colleges, November 1994)

### Exercise 25

Eight runners were convinced that the mean difference in their individual times for running one mile versus race walking one mile was at most 2 minutes. Below are their times. Do you agree that the mean difference is at most 2 minutes?

 Running time (minutes) Race walking time (minutes) 5.1 7.3 5.6 9.2 6.2 10.4 4.8 6.9 7.1 8.9 4.2 9.5 6.1 9.4 4.4 7.9

#### Solution

• d. t 7 t 7 size 12{t rSub { size 8{7} } } {}
• e. t = 2 . 9850 t = 2 . 9850 size 12{t=2 "." "9850"} {}
• f. 0.0102
• h. Decision: Reject null; There is sufficient evidence to conclude that the mean difference is more than 2 minutes.

### Exercise 26

Marketing companies have collected data implying that teenage girls use more ring tones on their cellular phones than teenage boys do. In one particular study of 40 randomly chosen teenage girls and boys (20 of each) with cellular phones, the mean number of ring tones for the girls was 3.2 with a standard deviation of 1.5. The mean for the boys was 1.7 with a standard deviation of 0.8. Conduct a hypothesis test to determine if the means are approximately the same or if the girls’ mean is higher than the boys’ mean.

### Exercise 27

While her husband spent 2½ hours picking out new speakers, a statistician decided to determine whether the percent of men who enjoy shopping for electronic equipment is higher than the percent of women who enjoy shopping for electronic equipment. The population was Saturday afternoon shoppers. Out of 67 men, 24 said they enjoyed the activity. 8 of the 24 women surveyed claimed to enjoy the activity. Interpret the results of the survey.

#### Solution

• e. 0.22
• f. 0.4133
• h. Decision: Do not reject null

### Exercise 28

We are interested in whether children’s educational computer software costs less, on average, than children’s entertainment software. 36 educational software titles were randomly picked from a catalog. The mean cost was $31.14 with a standard deviation of$4.69. 35 entertainment software titles were randomly picked from the same catalog. The mean cost was $33.86 with a standard deviation of$10.87. Decide whether children’s educational software costs less, on average, than children’s entertainment software. (Source: Educational Resources, December catalog)

### Exercise 31

Joan Nguyen recently claimed that the proportion of college–age males with at least one pierced ear is as high as the proportion of college–age females. She conducted a survey in her classes. Out of 107 males, 20 had at least one pierced ear. Out of 92 females, 47 had at least one pierced ear. Do you believe that the proportion of males has reached the proportion of females?

#### Solution

• e. -4.82
• f. 0
• h. Decision: Reject null

### Exercise 32

Some manufacturers claim that non-hybrid sedan cars have a lower mean miles per gallon (mpg) than hybrid ones. Suppose that consumers test 21 hybrid sedans and get a mean of 31 mpg with a standard deviation of 7 mpg. Thirty-one non-hybrid sedans get a mean of 22 mpg with a standard deviation of 4 mpg. Suppose that the population standard deviations are known to be 6 and 3, respectively. Conduct a hypothesis test to the manufacturers claim.

### Exercise 33

Using the data from Lap 1 only, conduct a hypothesis test to determine if the mean time for completing a lap in races is the same as it is in practices.

#### Solution

• d. t 20 . 32 t 20 . 32 size 12{t rSub { size 8{"20" "." "32"} } } {}
• e. -4.70
• f. 0.0001
• h. Decision: Reject null

### Exercise 34

Repeat the test in Exercise 33, but use Lap 5 data this time.

### Exercise 35

Repeat the test in Exercise 33, but this time combine the data from Laps 1 and 5.

#### Solution

• d. t 40 . 94 t 40 . 94 size 12{t rSub { size 8{"40" "." "94"} } } {}
• e. -5.08
• f. 0
• h. Decision: Reject null

### Exercise 36

In 2 – 3 complete sentences, explain in detail how you might use Terri Vogel’s data to answer the following question. “Does Terri Vogel drive faster in races than she does in practices?”

### Exercise 37

Is the proportion of race laps Terri completes slower than 130 seconds less than the proportion of practice laps she completes slower than 135 seconds?

#### Solution

• e. -0.9223
• f. 0.1782
• h. Decision: Do not reject null

### Exercise 38

"To Breakfast or Not to Breakfast?" by Richard Ayore

In the American society, birthdays are one of those days that everyone looks forward to. People of different ages and peer groups gather to mark the 18th, 20th, … birthdays. During this time, one looks back to see what he or she had achieved for the past year, and also focuses ahead for more to come.

If, by any chance, I am invited to one of these parties, my experience is always different. Instead of dancing around with my friends while the music is booming, I get carried away by memories of my family back home in Kenya. I remember the good times I had with my brothers and sister while we did our daily routine.

Every morning, I remember we went to the shamba (garden) to weed our crops. I remember one day arguing with my brother as to why he always remained behind just to join us an hour later. In his defense, he said that he preferred waiting for breakfast before he came to weed. He said, “This is why I always work more hours than you guys!”

And so, to prove his wrong or right, we decided to give it a try. One day we went to work as usual without breakfast, and recorded the time we could work before getting tired and stopping. On the next day, we all ate breakfast before going to work. We recorded how long we worked again before getting tired and stopping. Of interest was our mean increase in work time. Though not sure, my brother insisted that it is more than two hours. Using the data below, solve our problem.

 Work hours with breakfast Work hours without breakfast 8 6 7 5 9 5 5 4 9 7 8 7 10 7 7 5 6 6 9 5

## Try these multiple choice questions.

For questions Exercise 39Exercise 40, use the following information.

A new AIDS prevention drugs was tried on a group of 224 HIV positive patients. Forty-five (45) patients developed AIDS after four years. In a control group of 224 HIV positive patients, 68 developed AIDS after four years. We want to test whether the method of treatment reduces the proportion of patients that develop AIDS after four years or if the proportions of the treated group and the untreated group stay the same.

Let the subscript tt size 12{t} {}= treated patient and utut size 12{ ital "ut"} {}= untreated patient.

### Exercise 39

The appropriate hypotheses are:

• A. Ho:pt<putHo:pt<put size 12{H rSub { size 8{o} } :p rSub { size 8{t} } <p rSub { size 8{ ital "ut"} } } {} and Ha:ptputHa:ptput size 12{H rSub { size 8{a} } :p rSub { size 8{t} } >= p rSub { size 8{ ital "ut"} } } {}
• B. Ho:ptputHo:ptput size 12{H rSub { size 8{o} } :p rSub { size 8{t} } <= p rSub { size 8{ ital "ut"} } } {} and Ha:pt>putHa:pt>put size 12{H rSub { size 8{a} } :p rSub { size 8{t} } >p rSub { size 8{ ital "ut"} } } {}
• C. Ho:pt=putHo:pt=put size 12{H rSub { size 8{o} } :p rSub { size 8{t} } =p rSub { size 8{ ital "ut"} } } {} and Ha:ptputHa:ptput size 12{H rSub { size 8{a} } :p rSub { size 8{t} } <> p rSub { size 8{ ital "ut"} } } {}
• D. Ho:pt=putHo:pt=put size 12{H rSub { size 8{o} } :p rSub { size 8{t} } =p rSub { size 8{ ital "ut"} } } {} and Ha:pt<putHa:pt<put size 12{H rSub { size 8{a} } :p rSub { size 8{t} } <p rSub { size 8{ ital "ut"} } } {}

D

### Exercise 40

If the pp -value is 0.0062 what is the conclusion (use α = 0.05 α = 0.05 size 12{α=5%} {} )?

• A. The method has no effect.
• B. There is sufficient evidence to conclude that the method reduces the proportion of HIV positive patients that develop AIDS after four years.
• C. There is sufficient evidence to conclude that the method increases the proportion of HIV positive patients that develop AIDS after four years.
• D. There is insufficient evidence to conclude that the method reduces the proportion of HIV positive patients that develop AIDS after four years.

B

### Exercise 41

Lesley E. Tan investigated the relationship between left-handedness and right-handedness and motor competence in preschool children. Random samples of 41 left-handers and 41 right-handers were given several tests of motor skills to determine if there is evidence of a difference between the children based on this experiment. The experiment produced the means and standard deviations shown below. Determine the appropriate test and best distribution to use for that test.

 Left-handed Right-handed Sample size 41 41 Sample mean 97.5 98.1 Sample standard deviation 17.5 19.2

• A. Two independent means, normal distribution
• B. Two independent means, student's-t distribution
• C. Matched or paired samples, student's-t distribution
• D. Two population proportions, normal distribution

#### Solution

B

For questions Exercise 42Exercise 43, use the following information.

An experiment is conducted to show that blood pressure can be consciously reduced in people trained in a “biofeedback exercise program.” Six (6) subjects were randomly selected and the blood pressure measurements were recorded before and after the training. The difference between blood pressures was calculated afterbeforeafterbefore size 12{ left ( ital "after" - ital "before" right )} {} producing the following results: x¯d=10.2x¯d=10.2 size 12{ {overline {x}} rSub { size 8{d} } = - "10" "." 2} {} sd=8.4sd=8.4 size 12{s rSub { size 8{d} } =8 "." 4} {}. Using the data, test the hypothesis that the blood pressure has decreased after the training,

### Exercise 42

The distribution for the test is

• A. t 5 t 5 size 12{t rSub { size 8{5} } } {}
• B. t 6 t 6 size 12{t rSub { size 8{6} } } {}
• C. N ( 10 . 2,8 . 4 ) N ( 10 . 2,8 . 4 ) size 12{N $$- "10" "." 2,8 "." 4$$ } {}
• D. N ( 10 . 2, 8 . 4 6 ) N ( 10 . 2, 8 . 4 6 ) size 12{N $$- "10" "." 2, { { size 8{8 "." 4} } over { size 8{ sqrt {6} } } }$$ } {}

A

### Exercise 43

If α=0.05α=0.05 size 12{a=0 "." "05"} {}, the pp size 12{p} {}-value and the conclusion are

• A. 0.0014; There is sufficient evidence to conclude that the blood pressure decreased after the training
• B. 0.0014; There is sufficient evidence to conclude that the blood pressure increased after the training
• C. 0.0155; There is sufficient evidence to conclude that the blood pressure decreased after the training
• D. 0.0155; There is sufficient evidence to conclude that the blood pressure increased after the training

#### Solution

C

For questions Exercise 44Exercise 45, use the following information.

The Eastern and Western Major League Soccer conferences have a new Reserve Division that allows new players to develop their skills. Data for a randomly picked date showed the following annual goals.

 Western Eastern Los Angeles 9 D.C. United 9 FC Dallas 3 Chicago 8 Chivas USA 4 Columbus 7 Real Salt Lake 3 New England 6 Colorado 4 MetroStars 5 San Jose 4 Kansas City 3

Conduct a hypothesis test to determine if the Western Reserve Division teams score, on average, fewer goals than the Eastern Reserve Division teams. Subscripts: 1 Western Reserve Division (W); 2 Eastern Reserve Division (E)

### Exercise 44

The exact distribution for the hypothesis test is:

• A. The normal distribution.
• B. The student's-t distribution.
• C. The uniform distribution.
• D. The exponential distribution.

B

### Exercise 45

If the level of significance is 0.05, the conclusion is:

• A. There is sufficient evidence to conclude that the W Division teams score, on average, fewer goals than the E teams.
• B. There is insufficient evidence to conclude that the W Division teams score, on average, more goals than the E teams.
• C. There is insufficient evidence to conclude that the W teams score, on average, fewer goals than the E teams score.
• D. Unable to determine.

#### Solution

C

Questions Exercise 46Exercise 48 refer to the following.

Neuroinvasive West Nile virus refers to a severe disease that affects a person’s nervous system . It is spread by the Culex species of mosquito. In the United States in 2010 there were 629 reported cases of neuroinvasive West Nile virus out of a total of 1021 reported cases and there were 486 neuroinvasive reported cases out of a total of 712 cases reported in 2011. Is the 2011 proportion of neuroinvasive West Nile virus cases more than the 2010 proportion of neuroinvasive West Nile virus cases? Using a 1% level of significance, conduct an appropriate hypothesis test. (Source: http:// http://www.cdc.gov/ncidod/dvbid/westnile/index.htm )

• “2011” subscript: 2011 group.
• “2010” subscript: 2010 group

### Exercise 46

This is:

• A. a test of two proportions
• B. a test of two independent means
• C. a test of a single mean
• D. a test of matched pairs.

A

### Exercise 47

An appropriate null hypothesis is:

• A. p 2011 p 2010 p 2011 p 2010 size 12{p rSub { size 8{ ital "drugless"} } <= p rSub { size 8{ ital "drug"} } } {}
• B. p 2011 p 2010 p 2011 p 2010 size 12{P rSub { size 8{ ital "drugless"} } >= P rSub { size 8{ ital "drug"} } } {}
• C. μ 2011 μ 2010 μ 2011 μ 2010 size 12{μ rSub { size 8{ ital "drugless"} } >= μ rSub { size 8{ ital "drug"} } } {}
• D. p 2011 > p 2010 p 2011 > p 2010 size 12{P rSub { size 8{ ital "drugless"} } >P rSub { size 8{ ital "drug"} } } {}

A

### Exercise 48

The pp size 12{p} {}-value is 0.0022. At a 1% level of significance, the appropriate conclusion is

• A. There is sufficient evidence to conclude that the proportion of people in the United States in 2011 that got neuroinvasive West Nile disease is less than the proportion of people in the United States in 2010 that got neuroinvasive West Nile disease.
• B. There is insufficient evidence to conclude that the proportion of people in the United States in 2011 that got neuroinvasive West Nile disease is more than the proportion of people in the United States in 2010 that got neuroinvasive West Nile disease.
• C. There is insufficient evidence to conclude that the proportion of people in the United States in 2011 that got neuroinvasive West Nile disease is less than the proportion of people in the United States in 2010 that got neuroinvasive West Nile disease.
• D. There is sufficient evidence to conclude that the proportion of people in the United States in 2011 that got neuroinvasive West Nile disease is more than the proportion of people in the United States in 2010 that got neuroinvasive West Nile disease.

#### Solution

D

Questions Exercise 49 and Exercise 50 refer to the following:

A golf instructor is interested in determining if her new technique for improving players’ golf scores is effective. She takes four (4) new students. She records their 18-holes scores before learning the technique and then after having taken her class. She conducts a hypothesis test. The data are as follows.

 Player 1 Player 2 Player 3 Player 4 Mean score before class 83 78 93 87 Mean score after class 80 80 86 86

### Exercise 49

This is:

• A. a test of two independent means
• B. a test of two proportions
• C. a test of a single proportion
• D. a test of matched pairs.

D

### Exercise 50

The correct decision is:

• A. Reject HoHo size 12{H rSub { size 8{o} } } {}
• B. Do not reject HoHo size 12{H rSub { size 8{o} } } {}

#### Solution

B

Questions Exercise 51 and Exercise 52 refer to the following:

Suppose a statistics instructor believes that there is no significant difference between the mean class scores of statistics day students on Exam 2 and statistics night students on Exam 2. She takes random samples from each of the populations. The mean and standard deviation for 35 statistics day students were 75.86 and 16.91. The mean and standard deviation for 37 statistics night students were 75.41 and 19.73. The “day” subscript refers to the statistics day students. The “night” subscript refers to the statistics night students.

### Exercise 51

An appropriate alternate hypothesis for the hypothesis test is:

• A. μ day > μ night μ day > μ night size 12{μ rSub { size 8{8:"30"} } >μ rSub { size 8{"11":"30"} } } {}
• B. μ day < μ night μ day < μ night size 12{μ rSub { size 8{8:"30"} } <μ rSub { size 8{"11":"30"} } } {}
• C. μ day = μ night μ day = μ night size 12{μ rSub { size 8{8:"30"} } =μ rSub { size 8{"11":"30"} } } {}
• D. μ day μ night μ day μ night size 12{μ rSub { size 8{8:"30"} } <> μ rSub { size 8{"11":"30"} } } {}

D

### Exercise 52

A concluding statement is:

• A. There is sufficient evidence to conclude that statistics night students mean on Exam 2 is better than the statistics day students mean on Exam 2.
• B. There is insufficient evidence to conclude that the statistics day students mean on Exam 2 is better than the statistics night students mean on Exam 2.
• C. There is insufficient evidence to conclude that there is a significant difference between the means of the statistics day students and night students on Exam 2.
• D. There is sufficient evidence to conclude that there is a significant difference between the means of the statistics day students and night students on Exam 2.

C

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