Use technology or a z-score table to answer the question. the scores on a memory test are normally distributed with a mean of 100 and a standard deviation of 25. consider a group of 400 people who take the test. how many people will score 90 or less?

About 138 people will score 90 or less.

We first find the z-score associated with this:
z = (X-μ)/σ = (90-100)/25 = -10/25 = -0.4

Using a z-table (http://www.z-table.com) we see that the proportion of scores less than this is 0.3446.

Multiplying this by 400,
0.3446(400) = 137.84 ≈ 138

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