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A professor is comparing the grade distribution in his class of 120 students to the historical...

  1. A professor is comparing the grade distribution in his class of 120 students to the historical distribution of grades. Use the data in the table below to determine whether the current grade distribution is different from the historical distribution. Write a sentence or two interpreting your results. Be sure to include the appropriate statistical evidence: test statistic used, degrees of freedom, value of the test statistic, and test statistic critical value. Use α = .05. (You do not have to do follow up procedure.)

Grade

Frequency

Historical Percentage

A

6

2%

B

28

15%

C

56

58%

D

18

7%

F

12

18%

math   Statistics-And-Probability   
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Answer #1

Ans:

Chi square test for goodness of fit:

Grade observed(fo) Percentage expected(fe) (fo-fe)^2/fe
A 6 2% 2.4 5.40
B 28 15% 18 5.56
C 56 58% 69.6 2.66
D 18 7% 8.4 10.97
F 12 18% 21.6 4.27
Total 120 1 120 28.85

Test statistic:

Chi square=28.85

df=5-1=4

critical chi square=CHIINV(0.05,4)=9.488

p-value=CHIDIST(28.85,4)=0.0000

As,p-value<0.05,we reject the null hypothesis.

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