Question

The length of a human pregnancy is approximately normally distributed with mean LaTeX: \muμ=266 days and standard deviation LaTeX: \sigmaσ=16 days. Given the values of LaTeX: \muμx-bar and LaTeX: \sigmaσx-bar found in the preceding questions, find the probability that a random sample of 36 pregnancies has a mean gestation period of 260 days or less. In other words, find P(x-bar LaTeX: \le≤ 260). Choose the best answer. Group of answer choices .0122 .0274 .3520 .0465

Answer 1

Given = 266, and = 16

To find the probability, we need to find the z scores.

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n = 60, To calculate P( X 260) = P(X < 260)

Z = (260 – 266)/[16/Sqrt(36)] = -2.9

The required probability, (Z = -2.9) from the normal distribution tables is = 0.0122 (Option 1)

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