A psychologist wants to estimate the standard deviation of IQ scores. It is widely believed that IQ scores follow a normal distribution. Her random sample of 20 IQ scores has a mean of 101.3 and a standard deviation of 16.9. Find the 90% confidence interval for the population standard deviation based on this sample. Then give its lower limit and upper limit. Carry your intermediate computations to at least three decimal places. Round your answers to at least two decimal places. (If necessary, consult a list of formulas.) Lower limit: Upper limit: ?