Track quiz

Look at the table first. Then eleven checks.

Ten ideas about a set of readings: one number, and two ways to draw it
Idea	How it goes
One for many	One figure can stand for a heap of readings. Many figures could.
The mean	Add all readings. Share the total equally.
The median	Sort first. Cross off both ends. The survivor has as many places before it as after it.
An even count	Two are left. The median is exactly halfway between them.
The mode	Count how often each reading appears. The tallest pile wins. Ties are fine.
An outlier	One far reading drags the mean. The median stays about where it was.
Choosing	The question decides: a share, a middle value, or the commonest value.
Dot plot	A dot plot gives each reading one dot on a number line.
The range	The range is the largest reading minus the smallest reading.
Double bars	A double-bar graph gives each item two bars, one for each group.

Five months of rain measured 90, 110, 100, 130 and 70 mm. What is the mean?

130 mm, the wettest month
100 mm
70 mm, the driest month

Four crates hold 2, 3, 4 and 6 mangoes. What is the mean?

3.75
3, with 3 left over
There is no mean, since no crate holds that many

Bus counts over five days: 12, 7, 15, 9, 11. What is the median?

15, the third number as written
10.8, the total shared out
11

A sixth day is added: 7, 9, 11, 12, 15, 20. What is the median?

11, the earlier of the two survivors
11.5
12, since you cannot have half a bus

Seven shoe sizes came in: 5, 6, 6, 7, 6, 8, 7. What is the mode?

6
3, since that size turned up three times
6.43, the share of the total

Runs off five overs were 4, 4, 5, 6, 6. How many modes are there?

One, the larger tied value
None, since no value appears three times
Two, namely 4 and 6

Six scores are 20, 22, 24, 26, 28, 30. The 30 becomes 90. What happens?

Both rise by 10
The mean goes from 25 to 35. The median stays 25
Neither moves

Five house prices in lakhs are 8, 9, 10, 11 and 400. Which one shows a usual price?

The median, which is 10
The mean, since it uses every price
The mean, which is 87.6

A dot plot has dots at 2, 3, 3, 3 and 8. How many readings are there?

The readings are 12, 8, 15 and 10. What is the range?

A double-bar graph has gridlines worth 10 votes each. One bar reaches 5 gridlines and the other reaches 3. How many more votes does the longer bar show?

Your textbook calls this Part II, Chapter 5, Connecting the Dots…. You have shared a total and crossed off both ends. You have watched an outlier pull the mean.

Next: Constructions and Tilings. Draw exactly what you are told to draw. Tile a floor with no gaps.

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