Question

The National Highway Traffic Safety Administration reported the percentage of traffic accidents occurring each day of the week. Assume that a sample of accidents provided the following data. Sunday= 64, Monday=53, Tuesday=55, Wednesday=49, Thursday=55, Friday=68, Saturday=76. Conduct a hypothesis test to determine if the proportion of traffic accidents is the same for each day of the week. What is the -value? Compute the value of the test statistic (to 3 decimals).

Answers

  1. Answer:

    Hence,

    a)

    Test statistic X^{2} = 9.269.  

    p value = 0.148

    b)

    Sunday=  15.23%, Monday= 12.62%, Tuesday= 13.10%, Wednesday=11.67%,

    Thursday= 13.10%, Friday= 16.19%, Saturday= 18.09%.

    Step-by-step explanation:

    a)

                        relative observed    Expected       Chi square

    Category   frequency(p)      O_{i}    Ei=total*p    (O-E)^{2} R^{2}_{i} =(O_{i} -E_{i} )^{2} /E_{i}

         1           0.142857143      64.0         60.00    16.00          0.267

        2           0.142857143      53.0       60.00     49.00         0.817

        3           0.142857143      55.0         60.00     25.00        0.417

        4           0.142857143      49.0       60.00     121.00        2.017

        5           0.142857143      55.0         60.00     25.00        0.417

        6           0.142857143      68.0         60.00     64.00        1.067

        7           0.142857143      76.0         60.00    256.00        4.267

      Total         1.000      420        420             556       9.269

    Test statistic X^{2} = 9.269.  

    p value = 0.148 from excel: chidist(9.269,6)  

    b)

    Percentage %= Frequency of traffic occur on category x 100 / Total number of frequency given.

    Category          Percentage%

    Sunday                   15.23%

    Monday                    12.62%

    Tuesday                   13.10%

    Wednesday           11.67%

    Thursday           13.10%

    Friday                   16.19%

    Saturday                   18.09%

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