Rivet holes are punched in steel beams. To ensure that the rivets will fit and that the joint will have adequate strength, it is necessary to control the standard deviation o the diameter, and measurements are made periodically. Ten measurements are made of nominally 1-inch-diameter holes, and the standard deviation is found to be 0.002 inches. What is the 95% confidence interval on the standard deviation? Required – confidence interval in the standard deviation → Chi-squared distribution. S = 0,002 in., n = 10,  = n – 1 = 9. 95% confidence level:  = 1-0.95 = 0.05.