You are trying to find out the percentage of hospitals that provide some free care. You know the distribution is mound shaped and symmetric. Based on a simple random sample of hospitals in seven major cities, you obtain the following percentages of hospitals that provide some free care:
57, 56, 55, 56, 66, 60, 60
From these, you find the standard deviation to be 4. Find a 90% confidence interval for the mean of the percentage of hospitals that provide some free care.