Solve by hand then By Minitab 4) An observed frequency distribution of exam scor

Question

Solve by hand then By Minitab

4) An observed frequency distribution of exam scores is as follows: Exam ScorelUnder 60 60- 69 70-79 80 89 90 100 Frequency 36 75 70 34 i) suming a normal distribution with u 75 and o 15, find the probability of a randomly selected subject belonging to each class. (Use boundaries of 59.5, 69.5, 79.5, 89.5, 100.) ii) Using the probabilities found in part i), find the expected frequency for each category iii) Use a 0.05 significance level to test the claim that the exam scores were randomly selected from a normally distributed population with 75 and o 315.

Explanation / Answer

for as we know that zscore =(X-mean)/std deviation

hence (i)

2)

for above test stat 10.8502 and 4 degree of freedom ; p value =0.0283

as p vlaue is less then 0.05 level we reject null hypothesis and can not conclude that scores were randomely selected from a normally distributed population with mean =75 and std deviation =15.

score frequency probabilty <60 36 0.1507 60-69 75 0.2062 70-79 85 0.2610 80-89 70 0.2152 >90 34 0.1669

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