Question

A standard achievement test has a mean of 50 and a standard deviation of 10. The scores are normally distributed. The test is administered to 800 people. Show your work.

How many scores are less than 45?

Answer 1

This is a normal distribution question with

P(x < 45.0)=?
The z-score at x = 45.0 is,

z = -0.5
This implies that

Test is administered to 800 People
n(scored less than 45) = n(total) * P(x < 45)
n(scored less than 45) = 0.3085 * 800 = 246.8
PS: you have to refer z score table to find the final probabilities.
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