Class width (N/mm2) | Frequency | Cumulative Frequency |
0 - 4.9 | 0 | 0 |
5 - 9.9 | 1 | 1 (= 0 + 1) |
10 - 14.9 | 4 | 5 (=0 +1 +4) |
15 - 19.9 | 6 | 11 (=0 + 1 + 4 + 6) |
20 - 24.9 | 5 | 16 (=0 + 1 + 4 + 6 + 5) |
25 - 29.9 | 3 | 19 (= 0 + 1 + 4 + 6 + 5 + 3) |
30 - 34.9 | 1 | 20 (=0 + 1 + 4 + 6 + 5 + 3 + 1) |
35 - 39.9 | 0 | 20 (=0 + 1 + 4 + 6 + 5 + 3 + 1 + 0) |
What would be:
i) The Median
ii) The Inter-quartile range
iii) How many bricks had a compressive strengthmore than 22 N/mm2?
I believe it to be:
i) There are 20 sizes of brick. The median is the 10thvalue. By using cumulative frequency (0+1+4=6) gives us the 10thvalue that is in the 15-19.9 class width. So, the median is 15-19.9.
ii) The interquartile range is 24 (upper quartile) – 15(lower quartile) = 9
iii) 20 – 13 = 7. 7 bricks have a compressive strength morethan 22 N/mm2
But I am not sure.
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