Question

A set of biology exam scores are normally distributed with a mean of 70 points and a standard deviation of 6

points. Let X represent the score on a randomly selected exam from this set.

MY

Co

Find P(X>61).

You may round your answer to two decimal places.

Answer 1

.69

Explanation:

Normalcdf (lower: 0, upper: 73, mean: 70, S.D.: 6) = .691462 --> .69

Answer 2

To two decimal places, we have 0.93

Explanation:

We start by calculating the z-score

Mathematically;

z-score = (x-mean)/SD

here, x = 61

mean = 70 and SD = 6

So, we have ;

z-score = (61-70)/6

z-score = -9/6 = -1.5

So we want to calculate the probability of z > -1.5

We use the standard normal distribution table for this

The answer here according to the table is 0.93319

To 2 decimal places, this is 0.93