Step 1 :To find the minimum height to be considered in the top 15% of tallest men, we need to find the z-score that corresponds to the 85th percentile. Using a standard normal distribution table or a z-score calculator, we find that the z-score for the 85th percentile is approximately 1.0.
Step 2 :We then use the formula for a z-score, which is: \(Z = \frac{X - \mu}{\sigma}\) where \(Z\) is the z-score, \(X\) is the value we're trying to find, \(\mu\) is the mean, and \(\sigma\) is the standard deviation.
Step 3 :Rearranging the formula to solve for \(X\) gives us: \(X = Z\sigma + \mu\)
Step 4 :Substituting the given values into the formula gives us: \(X = 1.0 * 3 + 68 = 71\) inches
Step 5 :\(\boxed{71}\) inches is the minimum height to be considered in the top 15% of tallest men.
Step 6 :To find the tallest height to be considered in the shortest 20% of men, we need to find the z-score that corresponds to the 20th percentile. Using a standard normal distribution table or a z-score calculator, we find that the z-score for the 20th percentile is approximately -0.8.
Step 7 :Substituting the given values into the formula gives us: \(X = -0.8 * 3 + 68 = 66.6\) inches
Step 8 :\(\boxed{66.6}\) inches is the tallest height to be considered in the shortest 20% of men.