The average length of a candy bar is 43 millimeters. The executive of a candy production company is concerned that the settings of the machine cutting the bars have changed. She takes a random sample of 100 candy bars and measures their lengths. The sample mean is 42.5 millimeters with a standard deviation of 1.2 millimeters. She wants to test if the average length of the candy bars has changed. What is the null hypothesis for this test?
1) The average length of the candy bars has changed.
2) The average length of the candy bars is less than 43 millimeters.
3) The average length of the candy bars is greater than 43 millimeters.
4) The average length of the candy bars is equal to 43 millimeters.
