The piston diameter of a certain hand pump is 0.5 inch . The manager determines that the diameters are normally distributed , with a mean of 0.5 inch and a standard deviation of 0.006 inch . After recalibrating the production machine , the manager randomly selects 24 pistons and determines that the standard deviation is 0.0042 inch Is there significant evidence for the manager to conclude that the standard deviation has decreased at the a = 0.10 level of significance