The ages of a group of 155 randomly selected adult females have a standard deviation of 16.8 years. Assume that the ages of female statistics students have less variation than ages of females in the general​ population, so let σ=16.8 years for the sample size calculation. How many female statistics student ages must be obtained in order to estimate the mean age of all female statistics​ students? Assume that we want 98​% confidence that the sample mean is within​ a one-half year of the population mean. Does it seem reasonable to assume that the ages of female statistics students have less variation than ages of females in the general​ population? The required sample size is?

The ages of a group of 120 randomly selected adult females have a standard deviation of 18.4 years. Assume that the ages of female statistics students have less variation than ages of females in the general​ population, so let σ=18.4 years for the sample size calculation. How many female statistics student ages must be obtained in order to estimate the mean age of all female statistics​ students? Assume that we want 99​% confidence that the sample mean is within​ one-half year of the population mean. Does it seem reasonable to assume that the ages of female statistics students have less variation than ages of females in the general​ population? What's the required sample size? Does it seem reasonable to assume that the ages of female statistics students have less variation than ages of females in the general​ population?

Suppose that the lengths of pregnancies are normally distributed with a mean of 271 days and a standard deviation of 10 days.  find the percentage of pregnancies that are longer than 254 days. For your intermediate computations, use four or more decimal places. Give your final answer to two decimal places (for example 98.23%).

The ages of a group of 146 randomly selected adult females have a standard deviation of 16.5 years. Assume that the ages of female statistics students have less variation than ages of females in the general​ population, so let σ=16.5 years for the sample size calculation. How many female statistics student ages must be obtained in order to estimate the mean age of all female statistics​ students? Assume that we want 90​% confidence that the sample mean is within​ one-half year of the population mean. Does it seem reasonable to assume that the ages of female statistics students have less variation than ages of females in the general​ population?