How many women must be randomly selected to estimate the mean weight of women in one age group? We want 90% confidence that the sample mean is within 3.7 lbs of the populations mean, and population standard deviation is known to be 28 lbs.

155 women must be randomly selected.

Step-by-step explanation:

We have that to find our level, that is the subtraction of 1 by the confidence interval divided by 2. So:

Now, we have to find z in the Z-table as such z has a p-value of .

That is z with a pvalue of , so Z = 1.645.

Now, find the margin of error M as such

In which is the standard deviation of the population and n is the size of the sample.

The population standard deviation is known to be 28 lbs.

This means that

We want 90% confidence that the sample mean is within 3.7 lbs of the populations mean. How many women must be sampled?

This is n for which M = 3.7. So

Rounding up:

155 women must be randomly selected.

step-by-step explanation: