StatisticsdrillInterquartile range
A statistics problem from Statisticsdrill. Solve it with one answer box, with a fresh sample on every attempt and the worked steps and spreadsheet function in the answer, and it is checked the moment you submit.
The task
A sample of 9 minutes to resolve a support ticket (minutes): 46, 35, 28, 23, 26, 17, 29, 36, 18. Find the interquartile range using the inclusive quartile method: sort the data, take Q1 at rank 1 + 0.25(n - 1) and Q3 at rank 1 + 0.75(n - 1), and interpolate linearly between neighboring values. Round to 2 decimal places.
What this problem teaches
The formula: IQR = Q3 - Q1. The IQR covers the middle half of the data, so one extreme value barely moves it, unlike the range or the standard deviation. QUARTILE.EXC uses a different rank and gives a different number.
A hint if you get stuck
IQR = Q3 - Q1. Each quartile uses the same ranking rule as the inclusive percentile, with p = 0.25 and p = 0.75.
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