Announcements for 82 upcoming engineering conferences were randomly picked from a stack of IEEE Spectrum magazines. The mean length of the conferences was 3.93 days. The population standard deviation is 1.21 days. Assume the underlying population is normal. + Part (a) + Part (b) Part (c) Construct a 95% confidence interval for the population mean length of engineering conferences. (i) State the confidence interval. (Round your answers to two decimal places.) (ii) Sketch the graph. (Round your answers to two decimal places. Enter your a/2 to three decimal places.) C.L. = O X (iii) Calculate the error bound. (Round your answer to two decimal places.) Additional Materials Reading Submit