The diameter of a spindle in a small motor is supposed to be 4.9 millimeters (mm) with a standard deviation of 0.15 mm. If the spindle is either too small or too large, the motor will not work properly. The manufacturer measures the diameter in a sample of 18 spindles to determine whether the mean diameter has moved away from the required measurement. Suppose the sample has an average diameter of 4.77 mm. Required:
What are the null and alternative hypotheses (H0 = null hypothesis and Ha = alternative hypothesis)?