Find the critical values for an 80% confidence interval using the chi-square distribution with 11 degrees of freedom. Round the answers to three decimal places. The critical values are and 84 Section Exercise IQ scores: Scores on an IQ test are normally distributed. A sample of 6 IQ scores had standard deviations - 11. (a) Construct an 80% confidence interval for the population standard deviation o. Round the answers to at least two decimal places. (b) The developer of the test claims that the population standard deviation is o =