1 st Hour : 79,67,91,93,76,55,61,87,84,72,97,64,51,72,73,74,82,66,69,87,77,80,75

Question

1 st Hour : 79,67,91,93,76,55,61,87,84,72,97,64,51,72,73,74,82,66,69,87,77,80,75,88,67,86,
60,59,53,84,73,77.

Suppose the instructor thought the dispersion of the grades looked like a normal
distribution. He hypothesized that the number of A and F grades each represented 10% of the class. The number of B and D grades each represented 25 % of the class, and the number of C grades represented 30% of the class.
Test the hypothesis at the 0.05 level that the 1 st hour's grades were distributed the way the instructor thought. Use the Chi Squared test.

Explanation / Answer

                                A                B              C                 D                 F                 Total

 

d.f=5-1=4

                                A                B              C                 D                 F                 Total

Observed 3 8 10 7 4 32 Expected 3.2 8 9.6 8 3.2 32

 

(O-E)^2/E 0.0125 0 0.0166667 0.125 0.2 0.3541667

d.f=5-1=4

            Look up the chi-square table with d.f 4 and .05 significance level   The critical value=9.488                         Therefore, do not reject the instructor's hypothesis.    

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