In: Statistics and Probability
Use the central limit theorem to solve the problem.
Quiz scores for Grammer 222 class are normally distributed with a mean of 60.5 and a standard deviation of 10.5.
1. If a student is chosen, find the probability that this student's score is at least 70.2?
2. If a sample of 22 students is randomly selected, find the probability that their mean score is at least 70.2?
Solution :
Given that ,
1) P(x 70.2) = 1 - P(x 70.2)
= 1 - P[(x - ) / (70.2 - 60.5) / 10.5]
= 1 - P(z 0.92)
= 1 - 0.8212
= 0.1788
2) = 60.5
= / n = 10.5 / 22 = 2.24
P( 70.2) = 1 - P( 70.2)
= 1 - P[( - ) / (70.2 - 60.5) / 2.24]
= 1 - P(z 4.33)
= 1 - 1
= 0