The addition of a new accelerator is claimed to reduce the drying time of latex paint by more than 4%. Several test samples were conducted with following percentage decrease in drying time. Suppose that the percentage reduce in drying time is normally distributed.
5.3 6.5 3.8 5.9 3.7 2.6 2.9 4.2
(a) Determine the 95% confidence interval for the true mean decrease in the drying time based on this sample. (Give your answers correct to two decimal places.)