Sizu Home › Calculators › Mean, Median and the Spread Behind a Bar
Opens on Chapter 13’s example: Tobias’s eleven repair bills, one of them a $900 restoration.
An average of averages
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How it works
The mean is the total ÷ the count; the median is the middle value once sorted. One huge value drags the mean but barely moves the median. The standard deviation measures the typical distance from the mean; 1.96 × SD ÷ √n is a rough 95% margin for the mean. Averaging two group averages ignores their sizes; weight each by its size instead.
From the book, Chapter 13. The bills total $1,495: a mean of $136 but a median of $60. Team B’s times have a standard deviation of 11.2 minutes, a margin of about ±4.9, and 5 over 35 minutes. Averaging 14 and 6 gives 10; weighting by 20 and 30 gives 9.2. Every chapter and its calculator →
Rounding is half up, the way the book rounds. Numbers can be typed as 1,450, $38, 12% or 2.5 million. Everything stays in your browser: no sign-up, nothing stored or sent.