1. ©G Dear 2010 – Not to be sold/Free to use
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Applied Mathematic
(Preliminary General 1)
Percentiles,
Deciles &
Quartiles
Stage 6 - Year 11
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©G Dear 2010 – Not to be sold/Free to use

2. *Percentiles, Deciles and Quartiles What’s all this about?
We want to know
the spread of the scores.
The 20th percentile is the score that
has 20% of the scores below it.
It is also known as the 2nd decile.
End of
Slide

3. *Percentiles, Deciles and Quartiles What’s all this about?
We want to know
the spread of the scores.
The 25th percentile is the score that
has 25% of the scores below it.
It is also known as the lower quartile or Q1.
End of
Slide

4. *Percentiles, Deciles and Quartiles What’s all this about?
We want to know
the spread of the scores.
The 75th percentile is the score that
has 25% of the scores below it.
It is also known as the upper quartile or Q3.
End of
Slide

5. *Percentiles, Deciles and Quartiles What’s all this about?
What’s the spread of the scores.
The 50th percentile is the score that
has 50% of the scores below it.
It is also known as the 5th decile or median .
End of
Slide

6. The spread of the middle 50% of scores.
Interquartile Range
The spread of the middle 50% of scores.
IQR = Q3 – Q1
Q3 = 75th percentile = 12
Median = 50th percentile = 11
(5th decile)
Q1 = 25th percentile = 10
IQR = 12
- 10
= 2
Small IQR 2 4 6 8 10 12 14 16 18 20
End of
Slide

7. The spread of the middle 50% of scores.
Interquartile Range
The spread of the middle 50% of scores.
IQR = Q3 – Q1
Q3 = 75th percentile = 13
Median = 50th percentile = 11
(5th decile)
Q1 = 25th percentile = 7
IQR = 13
- 7
= 6
Medium IQR 2 4 6 8 10 12 14 16 18 20
End of
Slide

8. The spread of the middle 50% of scores.
Interquartile Range
The spread of the middle 50% of scores.
IQR = Q3 – Q1
Q3 = 75th percentile = 18
Median = 50th percentile = 11
(5th decile)
Q1 = 25th percentile = 3
IQR = 18
- 3
= 15
Large IQR 2 4 6 8 10 12 14 16 18 20
End of
Show