Level N Mean StDev A 7 85.739 5.085 B 5 76.167 6.555 C 5 80.000 9.230 D 7 69.333 6.154 Source DF SS MS F P Groups 3 980.58 326.86 7.30 0.002 Error 20 895.02 44.75 Total 23 1875.60 What is the pooled standard deviation? What degrees of freedom are used in doing inferences for these means and differences in means? Round your answer for the pooled standard deviation to two decimal places