The data to the right represent the age in weeks at which ba

The data to the right represent the age (in weeks) at which babies first crawl based on a survey of 12 mothers. It is known that the data are normally distributed and that s= 11.54 weeks. Construct a 90% confidence interval for the population standard deviation of the age (in weeks) at which babies first crawl. The 90% confidence interval is

Solution

Answer is (19.74, 57.66)

x	30	44	44	34	23	52	47	37	44	24	55	21	37.91667
x^2	900	1936	1936	1156	529	2704	2209	1369	1936	576	3025	441	1559.75
							Hence var(x) =	122.0764
							Std dev		11.04882
							Margin of error	18.17531
							conf int lb	19.74136
							ub		57.65803