Final answer:
The estimate of the standard deviation of the heights is 28 inches.
Step-by-step explanation:
To estimate the standard deviation of the heights in this population, we can use the fact that 99.7% of the heights fall between 50 inches and 7 feet (which is 84 inches). We know that this range represents three standard deviations, so we can set up the equation: 3 standard deviations = 84 inches. To find the standard deviation, we divide 84 inches by 3, which equals 28 inches. Therefore, our estimate of the standard deviation of the heights in this population is 28 inches.