Assume that the drying time for certain type of paint under specified test situations is known to be normally distributed with mean 75 minutes and standard deviation 5 minutes. Suppose also that chemists have devised a new additive that they hope will reduce the mean drying time (without changing the standard deviation). A test is then conducted to measure the drying time for a test specimen, and the company executives decide that they will be convinced that the additive is effective only if the drying time on this specimen is less than
70 minutes.
1. If you want to alter the cutoff value from 70 in order to reduce the error probability in part a to .05, what cutoff value should you choose?