The slant shear test is widely accepted for evaluating the bond of resinous repair materials to concrete; it utilizes cylinder specimens made of two identical halves bonded at 30°. The article “Testing the Bond Between Repair Materials and Concrete Substrate” (ACI Materials J., 1996:

553–558) reported that for 12 specimens prepared using wire-brushing, the sample mean shear strength (N/mm2

) and sample standard deviation were 19.20 and 1.58, respectively, whereas for 12 hand-chiseled specimens, the corresponding values were 23.13 and 4.01. Does the true average strength appear to be different for the two methods of surface preparation? State and test the relevant hypotheses using a significance level of .05. What are you assuming about the shear strength distributions?