The ends of two fixed rods A and B are each made in the form of a single-threaded screw of mean radius 6 mm and pitch 2 mm. Rod A has a right-handed thread and rod B has a left-handed thread. The coefficient of static friction between the rods and the threaded sleeve is 0.12. Determine the magnitude of the couple that must be applied to the sleeve in order to draw the rods closer together.

4.3.2 WILCOXON SIGNED-RANK TEST 1) Used for the differences between two samples. In this case we take the differences (D’s) and test the null hypothesis a. H :0Distribution of D’s is symmetric about the nullval∆e against the alternatives of D ▯ values tending to be smaller than▯ or D values tending to be larger th∆n▯ b. Rank the absolute values of the differences c. Calculate the test statistis+, by adding all off differences 2) Note: 3) The test statistic, denoted by W: 4) The null is rejected if 4.3.3 LEVENES TEST FOR VARIANCES 1) Used for comparing more than 2 population variations a. Deals with variances