Question

What is the probability that a randomly selected male will have a foot length between 8 and 12.5 inches? P(8 < r < 12.5)= ____ or ____%

Answer 1

Answer:

0.8185 or 81.85%

Step-by-step explanation:

The mean length (μ) of an adult foot is 11 and the standard deviation (σ) is 1.5.

The z score is a measure in statistic used to determine the amount of standard deviation by which the raw score (x) is above or below the mean. If the raw score is above the mean, the z score is positive  and if the raw score is below the mean the z sore is negative. It is given by:

$z=\frac{x-\mu}{\sigma}$

To calculate the probability that a randomly selected male will have a foot length between 8 and 12.5 inches, we first calculate the z score for 8 inches and then for 12.5 inches.

For 8 inches:

$z=\frac{x-\mu}{\sigma}=\frac{8-11}{1.5}=-2$

For 12.5 inches:

$z=\frac{x-\mu}{\sigma}=\frac{12.5-11}{1.5}=1$

From the normal distribution table, The probability that a randomly selected male will have a foot length between 8 and 12.5 inches = P(8 < x < 12.5) = P(-2 < z < 1) = P(z < 1)  - P(z < -2) = 0.8413 - 0.0228 = 0.8185 = 81.85%