Scores on a test are normally distributed with a mean of 68.9 and a standard dev

Question

Scores on a test are normally distributed with a mean of 68.9 and a standard deviation of 11.6. Find 81st percentile, which separates the bottom 81% from the top 19%. A) 0.88 B) 723 C) 79.1 D) 0291 A bank's loan officer rates applicants for credit. The ratings are normally distributed with a mean of 200 and a standard deviation of 50. Find 60th percentile, the score which separates the lower 60% from the top 40%. A) 212.5 B) 207.8 C) 2113 D) 1873 The amount of rainfall in January in a certain city is normally distributed with a mean of 4.9 inches and a standard deviation of 0.3 inches. Find the value of the quartile Q_1. A) 4.7 B) 4.8 C)1.2 D) 5.1 Assume that women have heights that are normally distributed with a mean of 63.6 inches and a standard deviation of 2.5 inches. Find the value of the quartile Q_3. A) 653 inches B) 66.1 inches C) 64.3 inches D) 67.8 inches The serum cholesterol levels for men in one age group are normally distributed with a mean of 177.9 and a standard deviation of 40.5. All units are in mg/100 mL. Find the two levels that separate the top 9% and the bottom 9%. A) 107.4 mg/100mL and248.4 mg/100mL B) 123.6 mg/100mL and232.2 mg/100mL C) 164.9 mg/100mL and 190.86 mg/100mL D) 161.3 mg/100mL and 194.5 mg/100mL Scores on an English test are normally distributed with a mean of 37.4 and a standard deviation of 7.9. Find the score that separates the top 59% from the bottom 41% A)392 B) 42.1 C) 32.7 D) 35.6

Explanation / Answer

Question 29

Mean is 68.9 and Standard deviation is 11.6

thus we need to find P(X<x)=0.81

which from the normal distribution table gives a z value of 0.88 (nearest p is 0.8106)

thus (x-68.9)/11.6 = 0.88 or x=11.6*0.88+68.9=79.1

which gives option c) as correct answer

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