Question

The data in the accompanying table represent the compressive strength, in thousands of pounds per square inch (psi), of 20 samples of concrete taken two and seven days after pouring. At the 0.05 level of significance, is there evidence that the mean strength is lower at two days than at seven days? Click the icon to view the data table. HAH70 C. Ho Hd 20 HA Hd < 0 HAHd > 0 O D. Ho 070 HAM = 0 Find the rejection region. Choose the correct answer below and fill in any answer boxes in your choice. (Round to four decimal places as needed.) O A. t< OB. t> O C. 1> ort

Answer 1

solution Here Ho - Md =0 vs Hild from the given data n=20 ret d= Iwo days - seven days. n 0-2796/520 7 Now a = Ed = -0.SUS3) · Sus3, Sd = 0.2796 Test statutic t= d -o sus3 -8.722 ed/n def=n-1=20-1=19 a=0.05 critical value =-). 7291 Reject Ho, if t <-1.7291 option (A) Here cal t =-8.722 L-17291 so, reject to