Question

2) In a set of data that show a normal distribution the mean is 7.8 and the standard deviation is 1.7. What is the proportion of numbers that are greater than 9? Show all work. (Hint: Find the z-score and use the z-table.)
Please help, I don't understand how to solve this question.

Answer 1

First, we get the z-score using formula:
z =( X - μ ) / σ

From the problem, we substitute the given values:
z = (9 - 7.8) / 1.7
z = 0.71

From the z-table (one-tailed), for a z-score of 0.7059, the proportion of numbers that are greater than 9 is  0.76.