Question

A teacher figures that final grades in the chemistry department are distributed as: A, 25%; B, 25%;C, 40%;D, 5%; F, 5%. At the end of a randomly selected semester, the following number of grades were recorded.

Grade	A	B	C	D	F
number of grade	42	36	60	14	8

a. Find the expected absences for each grade  If you have multiple answer, use comma to seperate each answer.

b. Use α= 0.01 to test the claim that the grade distribution has changed.

H0

H1

P-value  

decision  

conclusion  

Answer 1

a)

	A	B	C	D	F	Total
Observed frequency	42	36	60	14	8	160
Expected Frequency	0.25*160=40	0.25*160=40	04*160=64	0.05*160=8	0.05*160=8
chi square contribution	0.1	0.4	0.25	4.5	0

b) We will be conducting Chi square test here

Grade distribution has not changed

Grade distribution has changed

Test statistic :

degree of freedom = number of category - 1 = 5 -1 =4

P value for chi square test = 0.2626

Since the P value > significance level 0.01, we shall reject the null hypothesis.

hence we have evidence to say that the Grade distribution has changed