Question

The salt content in snack bags of pretzels is Normally distributed, with a mean of 180 mg and a standard deviation of 15 mg. Eighty four percent of bags have a salt content higher than which value?
Find the z-table here.


165.2 mg

179.2 mg

187.0 mg

194.9 mg

I think its (A), 165.2mg

Answer 1

Answer: Yes you are correct. The answer is choice A

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Explanation:

If you used the z-table, you should find that P(Z < 1) = 0.84 approximately.

So by symmetry, P(Z > -1) = 0.84 approximately as well.

We'll convert the z score z = -1 into its corresponding x score

z = (x-mu)/sigma

-1 = (x-180)/15

-15 = x-180

x-180 = -15

x = -15+180

x = 165

We don't land on any of the answer choices listed, but we get fairly close to 165.2, which is choice A. So you are correct.

I have a feeling that the table you have is probably more accurate than the one I'm using, so it's possible that you'd land exactly on 165.2 when following the steps above.