Step 1 :Given that women's heights are normally distributed with a mean of 63.4 inches and a standard deviation of 2.4 inches.
Step 2 :The height requirement for a branch of the military is between 58 inches and 80 inches.
Step 3 :We need to find the percentage of women who meet this height requirement.
Step 4 :This is a problem of finding the probability that a normally distributed random variable falls within a certain range.
Step 5 :We can use the cumulative distribution function (CDF) of the normal distribution to solve this problem.
Step 6 :The CDF at a point x gives the probability that the random variable is less than or equal to x.
Step 7 :So, to find the probability that the height is between 58 and 80 inches, we need to find the difference between the CDF at 80 and the CDF at 58.
Step 8 :Calculating the z-scores for the lower and upper bounds, we get \(z_{lower} = -2.25\) and \(z_{upper} = 6.92\).
Step 9 :Using these z-scores, we find the probabilities \(p_{lower} = 0.0122\) and \(p_{upper} = 1.00\).
Step 10 :The probability that a woman's height is between 58 and 80 inches is the difference between these two probabilities, which is \(p_{between} = 0.9878\).
Step 11 :This means that approximately 98.78% of women meet the height requirement.
Step 12 :So, only a small percentage of women are not allowed to join this branch of the military because of their height.
Step 13 :Final Answer: \(\boxed{\text{D. No, because only a small percentage of women are not allowed to join this branch of the military because of their height.}}\)