Psychologists often measure how long it takes mice to find their way through a maze. The times for one particular maze follow an approximately Normal distribution with mean 18 seconds and standard deviation 3 seconds. A researcher thinks that a loud noise will cause mice to complete the maze faster (but not change the standard deviation). She uses a loud noise to stimulate each of 10 mice right before she measures how long it takes each of them to complete the maze. The sample mean is = 16.2 seconds. The appropriate null and alternative hypotheses for this test are Ho = 18 seconds, Ha: < 18 seconds. The sample result is a) not statistically significant at any level. b) statistically significant at the 5% level, but not at the 2% level. c) proves that the mean time after a loud noise has changed to 116.2 seconds.