GCSE Maths revision · Higher: probability and statistics
A box plot shows the minimum, lower quartile, median, upper quartile and maximum. To compare two distributions, compare a median (average) and an interquartile range (spread), in context.
Watch out A comparison needs both an average and a spread, each with its meaning.
Here are the times, in minutes, of 11 runners, in order: 3, 5, 6, 8, 9, 11, 12, 14, 15, 18, 21.
Work out the interquartile range.
Answer 9 minutes
These twelve scores are in ascending order. 2, 5, 7, 8, 10, 13, 15, 16, 20, 22, 25, 30 Take the lower quartile to be the median of the lower six scores. What is the lower quartile?
The ordered data are 2, 4, 7, 9, 12, 14, 16, 20. Take Q1 as the median of the lower four values and Q3 as the median of the upper four values.
(a) Find the interquartile range.
(b) Find the median.
A box plot has minimum 5 and median 20. The interquartile range is 12 and the range is 30. The distance from the median to the upper quartile is twice the distance from the lower quartile to the median.
(a) Work out the lower quartile.
(b) Work out the maximum value.
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