Box and Whisker Data Analysis

Question

This is a Statistics question which uses Box and Whisker Plots.

This is the question:

Number of days of rainfall in a year:

39, 46, 26, 12, 34, 57, 38, 37, 69, 15, 44, 47, 38, 58, 75, 29, 40, 35, 22, 69, 22, 37, 51, 55, 46, 27, 19, 36, 72, 49

What percent of the rainfall is greater than 39 inches?

End Question

I don't understand how to do this, I created a Box And Whisker plot, but 39 isn't one of the key values. How do I find the percentage?

Answer 1

Comment: Here are your 30 observations sorted from smallest to largest:

sort(x)
 [1]   12 15 19 22 22 26 27 29 34 35 36 37 37 38 38 39
[17]   40 44 46 46 47 49 51 55 57 58 69 69 72 75

So 14 of them are larger than 39. What percentage is that?

I think you are correct that this problem is not obviously connected to boxplots. Here is a boxplot of your rainfall observations from R statistical software.

The five key numbers represented in the boxplot are: 12.0 (left end of lower whisker) 29.0 (left end of box), 38.5 (median: solid line within box), 51.0 (right end of box), and 75.0 (right end of right whisker).

Various books and statistical softwares have slightly different versions of how to get some of these five numbers. It may be worthwhile noticing that 39 is very close to the median, so slightly less than half of the observations are above 39.