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9.7: Chapter 12 Homework

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    12.1 Test of Two Variances

    55.

    Three students, Linda, Tuan, and Javier, are given five laboratory rats each for a nutritional experiment. Each rat’s weight is recorded in grams. Linda feeds her rats Formula A, Tuan feeds his rats Formula B, and Javier feeds his rats Formula C. At the end of a specified time period, each rat is weighed again and the net gain in grams is recorded.

    Linda's ratsTuan's ratsJavier's rats
    43.547.051.2
    39.440.540.9
    41.338.937.9
    46.046.345.0
    38.244.248.6
    Table \(\PageIndex{18}\)

    Determine whether or not the variance in weight gain is statistically the same among Javier’s and Linda’s rats. Test at a significance level of 10%.

    56.

    A grassroots group opposed to a proposed increase in the gas tax claimed that the increase would hurt working-class people the most, since they commute the farthest to work. Suppose that the group randomly surveyed 24 individuals and asked them their daily one-way commuting mileage. The results are as follows.

    Working-classProfessional (middle incomes)Professional (wealthy)
    17.816.58.5
    26.717.46.3
    49.422.04.6
    9.47.412.6
    65.49.411.0
    47.12.128.6
    19.56.415.4
    51.213.99.3
    Table \(\PageIndex{19}\)

    Determine whether or not the variance in mileage driven is statistically the same among the working class and professional (middle income) groups. Use a 5% significance level.

    Use the following information to answer the next two exercises. The following table lists the number of pages in four different types of magazines.

    Home decoratingNewsHealthComputer
    1728782104
    28694153136
    1631238798
    205106103207
    19710196146
    Table \(\PageIndex{20}\)
    57.

    Which two magazine types do you think have the same variance in length?

    58.

    Which two magazine types do you think have different variances in length?

    59.

    Is the variance for the amount of money, in dollars, that shoppers spend on Saturdays at the mall the same as the variance for the amount of money that shoppers spend on Sundays at the mall? Suppose that the Table \(\PageIndex{21}\) shows the results of a study.

    SaturdaySundaySaturdaySunday
    754462137
    1858082
    1506112439
    941950127
    629931141
    736011873
     89    

    Table 12.21

    60.

    Are the variances for incomes on the East Coast and the West Coast the same? Suppose that Table \(\PageIndex{22}\) shows the results of a study. Income is shown in thousands of dollars. Assume that both distributions are normal. Use a level of significance of 0.05.

    EastWest
    3871
    47126
    3042
    8251
    7544
    5290
    11588
    67  
    Table \(\PageIndex{22}\)
    61.

    Thirty men in college were taught a method of finger tapping. They were randomly assigned to three groups of ten, with each receiving one of three doses of caffeine: 0 mg, 100 mg, 200 mg. This is approximately the amount in no, one, or two cups of coffee. Two hours after ingesting the caffeine, the men had the rate of finger tapping per minute recorded. The experiment was double blind, so neither the recorders nor the students knew which group they were in. Does caffeine affect the rate of tapping, and if so how?

    Here are the data:

    0 mg100 mg200 mg0 mg100 mg200 mg
    242248246245246248
    244245250248247252
    247248248248250250
    242247246244246248
    246243245242244250

    Table 12.23

    62.

    King Manuel I, Komnenus ruled the Byzantine Empire from Constantinople (Istanbul) during the years 1145 to 1180 A.D. The empire was very powerful during his reign, but declined significantly afterwards. Coins minted during his era were found in Cyprus, an island in the eastern Mediterranean Sea. Nine coins were from his first coinage, seven from the second, four from the third, and seven from a fourth. These spanned most of his reign. We have data on the silver content of the coins:

    First coinageSecond coinageThird coinageFourth coinage
    5.96.94.95.3
    6.89.05.55.6
    6.46.64.65.5
    7.08.14.55.1
    6.69.3  6.2
    7.79.2  5.8
    7.28.6  5.8
    6.9      
    6.2      
    Table \(\PageIndex{24}\)

    Did the silver content of the coins change over the course of Manuel’s reign?

    Here are the means and variances of each coinage. The data are unbalanced.

     FirstSecondThirdFourth
    Mean6.74448.24294.8755.6143
    Variance0.29531.20950.20250.1314

    Table 12.25

    63.

    The American League and the National League of Major League Baseball are each divided into three divisions: East, Central, and West. Many years, fans talk about some divisions being stronger (having better teams) than other divisions. This may have consequences for the postseason. For instance, in 2012 Tampa Bay won 90 games and did not play in the postseason, while Detroit won only 88 and did play in the postseason. This may have been an oddity, but is there good evidence that in the 2012 season, the American League divisions were significantly different in overall records? Use the following data to test whether the mean number of wins per team in the three American League divisions were the same or not. Note that the data are not balanced, as two divisions had five teams, while one had only four.

    DivisionTeamWins
    EastNY Yankees95
    EastBaltimore93
    EastTampa Bay90
    EastToronto73
    EastBoston69
    Table \(\PageIndex{26}\)
    DivisionTeamWins
    CentralDetroit88
    CentralChicago Sox85
    CentralKansas City72
    CentralCleveland68
    CentralMinnesota66
    Table \(\PageIndex{27}\)
    DivisionTeamWins
    WestOakland94
    WestTexas93
    WestLA Angels89
    WestSeattle75
    Table \(\PageIndex{28}\)

    12.2 One-Way ANOVA

    64.

    Three different traffic routes are tested for mean driving time. The entries in the Table \(\PageIndex{29}\) are the driving times in minutes on the three different routes.

    Route 1Route 2Route 3
    302716
    322941
    272822
    353631
    Table \(\PageIndex{29}\)

    State \(SS_{between}\), \(SS_{within}\), and the \(F\) statistic.

    65.

    Suppose a group is interested in determining whether teenagers obtain their drivers licenses at approximately the same average age across the country. Suppose that the following data are randomly collected from five teenagers in each region of the country. The numbers represent the age at which teenagers obtained their drivers licenses.

     NortheastSouthWestCentralEast
     16.316.916.416.217.1
     16.116.516.516.617.2
     16.416.416.616.516.6
     16.516.216.116.416.8
    \(\overline x\)=________________________________________
    \(s^2=\)________________________________________
    Table \(\PageIndex{30}\)

    State the hypotheses.

    \(H_0\): ____________

    \(H_a\): ____________

    12.3 The F Distribution and the F-Ratio

    Use the following information to answer the next three exercises. Suppose a group is interested in determining whether teenagers obtain their drivers licenses at approximately the same average age across the country. Suppose that the following data are randomly collected from five teenagers in each region of the country. The numbers represent the age at which teenagers obtained their drivers licenses.

     NortheastSouthWestCentralEast
     16.316.916.416.217.1
     16.116.516.516.617.2
     16.416.416.616.516.6
     16.516.216.116.416.8
    \(\overline x\)=________________________________________
    \(s^2=\)________________________________________
    Table \(\PageIndex{31}\)

    \(H_{0} : \mu_{1}=\mu_{2}=\mu_{3}=\mu_{4}=\mu_{5}\)

    \(H_a\): At least any two of the group means \(\mu_{1}=\mu_{2}=\mu_{3}=\mu_{4}=\mu_{5}\) are not equal.

    66.

    degrees of freedom – numerator: \(df(num)\) = _________

    67.

    degrees of freedom – denominator: \(df(denom)\) = ________

    68.

    \(F\) statistic = ________

    12.4 Facts About the F Distribution

    69.

    Three students, Linda, Tuan, and Javier, are given five laboratory rats each for a nutritional experiment. Each rat's weight is recorded in grams. Linda feeds her rats Formula A, Tuan feeds his rats Formula B, and Javier feeds his rats Formula C. At the end of a specified time period, each rat is weighed again, and the net gain in grams is recorded. Using a significance level of 10%, test the hypothesis that the three formulas produce the same mean weight gain.

    Linda's ratsTuan's ratsJavier's rats
    43.547.051.2
    39.440.540.9
    41.338.937.9
    46.046.345.0
    38.244.248.6
    Table \(\PageIndex{32}\) Weights of Student Lab Rats
    70.

    A grassroots group opposed to a proposed increase in the gas tax claimed that the increase would hurt working-class people the most, since they commute the farthest to work. Suppose that the group randomly surveyed 24 individuals and asked them their daily one-way commuting mileage. The results are in Table \(\PageIndex{33}\). Using a 5% significance level, test the hypothesis that the three mean commuting mileages are the same.

    Working-classProfessional (middle incomes)Professional (wealthy)
    17.816.58.5
    26.717.46.3
    49.422.04.6
    9.47.412.6
    65.49.411.0
    47.12.128.6
    19.56.415.4
    51.213.99.3

    Table 12.33

    Use the following information to answer the next two exercises. Table \(\PageIndex{34}\) lists the number of pages in four different types of magazines.

    Home decoratingNewsHealthComputer
    1728782104
    28694153136
    1631238798
    205106103207
    19710196146
    Table \(\PageIndex{34}\)
    71.

    Using a significance level of 5%, test the hypothesis that the four magazine types have the same mean length.

    72.

    Eliminate one magazine type that you now feel has a mean length different from the others. Redo the hypothesis test, testing that the remaining three means are statistically the same. Use a new solution sheet. Based on this test, are the mean lengths for the remaining three magazines statistically the same?

    73.

    A researcher wants to know if the mean times (in minutes) that people watch their favorite news station are the same. Suppose that Table \(\PageIndex{35}\) shows the results of a study.

    CNNFOXLocal
    451572
    124337
    186856
    385060
    233151
    3522  
    Table \(\PageIndex{35}\)

    Assume that all distributions are normal, the four population standard deviations are approximately the same, and the data were collected independently and randomly. Use a level of significance of 0.05.

    74.

    Are the means for the final exams the same for all statistics class delivery types? Table \(\PageIndex{36}\) shows the scores on final exams from several randomly selected classes that used the different delivery types.

    OnlineHybridFace-to-Face
    728380
    847378
    778484
    808181
    81  86
       79
       82
    Table \(\PageIndex{36}\)

    Assume that all distributions are normal, the four population standard deviations are approximately the same, and the data were collected independently and randomly. Use a level of significance of 0.05.

    75.

    Are the mean number of times a month a person eats out the same for whites, blacks, Hispanics and Asians? Suppose that TableTable \(\PageIndex{38}\) shows the results of a study.

    PowderMachine MadeHard Packed
    1,2102,1072,846
    1,0801,1491,638
    1,5378622,019
    9411,8701,178
     1,5282,233
     1,382  
    Table \(\PageIndex{38}\)

    Assume that all distributions are normal, the four population standard deviations are approximately the same, and the data were collected independently and randomly. Use a level of significance of 0.05.

    77.

    Sanjay made identical paper airplanes out of three different weights of paper, light, medium and heavy. He made four airplanes from each of the weights, and launched them himself across the room. Here are the distances (in meters) that his planes flew.

    Paper type/TrialTrial 1Trial 2Trial 3Trial 4
    Heavy5.1 meters3.1 meters4.7 meters5.3 meters
    Medium4 meters3.5 meters4.5 meters6.1 meters
    Light3.1 meters3.3 meters2.1 meters1.9 meters

    Table 12.39

    the graph is a scatter plot which represents the data provided. The horizontal axis is labeled 'Distance in Meters,' and extends form 2 to 6. The vertical axis is labeled 'Weight of Paper' and has light, medium, and heavy categories. Figure \(\PageIndex{8}\)
    1. An experiment was conducted on the number of eggs (fecundity) laid by female fruit flies. There are three groups of flies. One group was bred to be resistant to DDT (the RS group). Another was bred to be especially susceptible to DDT (SS). Finally there was a control line of non-selected or typical fruitflies (NS). Here are the data:
      RSSSNSRSSSNS
      12.838.435.422.423.122.6
      21.632.927.427.529.440.4
      14.848.519.320.31634.4
      23.120.941.838.720.130.4
      34.611.620.326.423.314.9
      19.722.337.623.722.951.8
      22.630.236.926.122.533.8
      29.633.437.329.515.137.9
      16.426.728.238.63129.5
      20.33923.444.416.942.4
      29.312.833.723.216.136.6
      14.914.629.223.610.847.4
      27.312.241.7      
      Table \(\PageIndex{40}\)

      Here is a chart of the three groups:

      This graph is a scatterplot which represents the data provided. The horizontal axis is labeled 'Mean eggs laid per day' and extends from 10 - 50. The vertical axis is labeled 'Fruitflies DDT resistant or susceptible, or not selected.' The vertical axis is labeled with the categories NS, RS, SS. Figure \(\PageIndex{9}\) 79.

      The data shown is the recorded body temperatures of 130 subjects as estimated from available histograms.

      Traditionally we are taught that the normal human body temperature is 98.6 F. This is not quite correct for everyone. Are the mean temperatures among the four groups different?

      Calculate 95% confidence intervals for the mean body temperature in each group and comment about the confidence intervals.

      FLFHMLMHFLFHMLMH
      96.496.896.396.998.498.698.198.6
      96.797.796.79798.798.698.198.6
      97.297.897.197.198.798.698.298.7
      97.297.997.297.198.798.798.298.8
      97.49897.397.498.798.798.298.8
      97.69897.497.598.898.898.298.8
      97.79897.497.698.898.898.398.9
      97.89897.497.798.898.898.499
      97.898.197.597.898.898.998.499
      97.998.397.697.999.29998.599
      97.998.397.69899.39998.599.2
      9898.397.898  99.198.699.5
      98.298.497.898  99.198.6  
      98.298.497.898.3  99.298.7  
      98.298.497.998.4  99.499.1  
      98.298.49898.4  99.999.3  
      98.298.59898.6  10099.4  
      98.298.69898.6  100.8    
      Table \(\PageIndex{41}\)

    9.7: Chapter 12 Homework is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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