Two groups (pre and post) of data are summarized below: Pre-Data Post-Data 68 66 74 52 67 63 77 57 80 74 58 77 53 76 54 73 54 69 63 60 77 63 60 68 64 68 73 66 71 66 55 71 84 64 76 63 73 59 68 64 82 (i) Using the same scales, obtain dotplots for each of the two data sets (ii) Comment on (compare) the centres and spread of the two dataset (iii) Construct a (back-to-back) stem-and-leaf diagram for these data (This is easy to research) (iv) Construct and interpret boxplots