Two machines, A and B, produce metal rods of a certain type. The lengths, in metres, of 19 rods produced by machine A and 19 rods produced by machine B are shown in the following back-to-back stem-and-leaf diagram. ``` A | | B 7 6 3 0 | 21 | 1 2 4 8 7 4 3 1 1 | 22 | 2 4 5 5 6 5 5 5 3 2 | 23 | 0 2 6 8 9 9 4 3 1 0 | 24 | 3 3 4 6 | 25 | 6 ``` Key: 7 | 22 | 4 means 0.227 m for machine A and 0.224 m for machine B.

1. (a)Find the median and the interquartile range for machine A.[3]
2. (b)It is given that for machine B the median is 0.232m, the lower quartile is 0.224 m and the upper quartile is 0.243 m. Draw box-and-whisker plots for A and B.[3]
3. (c)Hence make two comparisons between the lengths of the rods produced by machine A and those produced by machine B.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.