A testing laboratory is trying to make its results more consistent by standardizing certain procedures. From a sample of size 28 the sample standard deviation by the revised procedure is found to be...

A testing laboratory is trying to make its results more consistent by standardizing certain procedures. From a sample of size 28 the sample standard deviation by the revised procedure is found to be 1.74 units. Plotting concentrations on normal probability paper did not show any marked departure from a normal distribution. Is there evidence at the 5% level of significance that the sample standard deviation is significantly less than the former population standard deviation of 2.92 units?