Scores on a test are normally distributed with a mean of 76 and a standard deviation of 6. Using the z-score table, estimate the probability a randomly selected student scored above 70

Question

a. 

1.20

b. 

0.2

c. 

0.98

d. 

0.84

Answer 1

A probability value can't be greater than 1, so we can eliminate choice a.

Since we want the probability for a z score of -1 and above (70 is one standard deviation below the mean), the probability must be greater than 0.5, so choice b is out.

P(z > -1) = P(z > 0) + P(-1 < z < 0) = 0.5 + 0.341 = 0.841