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Maths · Grade 6 · Set A
Which Number Tells the Story?
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A
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Goal: 15 min
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Remember: Look at the dots first. A far dot pulls the mean, so use the median. Balanced dots let you use the mean.

Mean or median?

1
The mean is a good measure of the typical value here.
TrueFalse
2
Compare the mean of this data with its median.
The mean is lowerAbout the sameThe mean is higher
3
Why is the mean a poor choice for a typical value here?
One far dot pulls itThe mean is never a good pickThere are too many dots
4
The median is the middle of the dots. What is the median of this data? Answer:
5
The top plot is Class A and the bottom plot is Class B. Which class should use the median?
Class AClass B

Spread, too

6
Which number shows the spread of the typical kids in this data?
The IQRThe range
7
Join each situation to the best number.
  1. 1Balanced dots, no far dot
  2. 2One dot far from the rest
  3. 3Spread that goes with the mean
  4. 4Spread that goes with the median
  • Athe mean
  • Bthe IQR
  • Cthe MAD
  • Dthe median
8
One far dot changes the median a lot.
TrueFalse
9
Class A's scores are shown. What is the mean score? Answer:
10
The three dot plots are A on top, B in the middle and C at the bottom. Which one is a good place to use the mean?
ABC

Stretch

11
The data is 1, 2, 2, 3 and 12. Take away the far dot. What is the mean of the four dots left? Answer:
12
For the data 1, 2, 2, 3 and 12, would you report the mean or the median as the typical value? Write why.
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Answer key · Set A
Which Number Tells the Story?
1True The dots are balanced and none is far from the rest, so the mean and the median agree.
2The mean is higher The median is 3. The far dot at 15 pulls the mean toward the big numbers: it is about 4.1.
3One far dot pulls it The mean uses every dot, so the far dot at 18 drags it up. The median stays with the crowd.
42 There are 8 dots. The 4th and 5th are both 2, so the median is 2.
5Class B Class B has one dot far from the rest. It pulls the mean away, so the median is the better pick.
6The IQR The range counts the far dot, so it is 17. The IQR, only 1.5, describes the middle half.
71-A, 2-D, 3-C, 4-B Mean and MAD go together for balanced data. Median and IQR go together when a far dot could mislead.
8False The median is the middle dot. A far dot does not move the middle.
96 The scores add to 54, and 54 ÷ 9 = 6.
10B B is balanced. A and C each have a dot far from the rest that would pull the mean.
112 1 + 2 + 2 + 3 = 8, and 8 ÷ 4 = 2. With the far dot the mean was 4, so one dot moved it a lot.
12Your own words: a grown-up reads it.
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