Answer:
Step-by-step explanation:
Complete Question:
Chapter 6, Section 1-D, Exercise 009 Is a Normal Distribution Appropriate? In each case below, is the sample size large enough so that the sample proportions follow a normal distribution?
a) n=600 p=0.2
b) n=20, p=0.4
if np=10 and npq=10 then the data follows normal distribution
a) np= 120,
q= 1-0.2= 0.8
npq= 600 ×0.2×0.4 = 48
Normal distribution is appropriate and sample size is large enough
b) np= 8
q= 1-0.4= 0.6
npq= 20 × 0.4×0.6= 4.8
sample size is not large enough so normal distribution is not appropriate.
Correct Answer:Option A. 0.01
Solution:This is a problem of statistics and uses the concept of normal distributions. We need to convert the score of 90 into z-score and then find the desired probability from standard normal distribution table.
Converting 90 to z-score:

Now we are to find the probability of z score being more than 2.33. From the z-table the probability comes out to be 0.01.
Therefore, we can conclude that the probability of class average is greater than 90 is 0.01.
I think it might be D. I'm just giving an educated guess.