An industrial designer wants to determine the average amount of time it takes an adult to assemble an “easy to assemble” toy. a sample of 16 times yielded an average time of 19.9 minutes, with a sample standard deviation of 6 minutes. assuming normality of assembly times, provide a 90% confidence interval for the mean assembly time.
a. (16.9, 22.9)b. (18.4, 21.4)c. (17.43, 22.37)d. (17.27, 22.53)