Lesson 2 of 11
The two sides always match
Show on a big screenThat was not a lucky pencil. What is really equal?
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Step 1 of 2
- Five overs, plotted. The mean sits at 6.
- Gaps below add to 6. The gap above is 6 too.
Measure the distances, not the count
Distance from the mean — how far a reading is from the mean. This is its gap.
Distances above the mean total the same as distances below it.
Take five overs of a cricket match. An over is a set of six balls. The overs gave 4, 6, 3, 12 and 5 runs. The runs add to 30. Shared five ways, 30 ÷ 5 = 6. So the mean is 6.
Each distance is the gap between a reading and 6. The distances are 2, 0, 3, 6 and 1. The 6 is on the mean. Its distance is 0. Three readings are below 6: 4, 3 and 5. One is above 6: 12.
Below: 2 + 3 + 1 = 6. Above: 6. The two sides match.
Try the lab to finish this lesson.