Relative Frequency

1
Relative Frequency

• And
• Pie Charts

2
What is to be learned?

• How to use relative frequencies to interpret Pie
  Charts
• How to use relative frequencies to draw Pie Charts

3
Types of Ice Cream

• Need to measure angles!

4
400
1000
800
1400

• Convert to relative frequencies
• 3600 altogether
• 100/360
• Do not convert nicely to percentages

140/360
PE
Art
5
400
1000
800
1400
If 270 people in survey, how many did PE? PE ?
140/360 140 360 X 270 105
of
270
X
Multiply by rel freq
6
Relative Frequency Calculations
I am a flower

• Usually tackled by
• Rel Freq X Total

How many thistles from 900 flowers?
Tulip
Rose
Rel freq 130/360
1050
1250
1300
No of thistles 130/360
X 900
Thistle
325
7
Drawing Pie Charts

• Need to calculate the angles
• Again use relative frequencies

8
Ronnie the rat
Another Exciting Survey
Pet Frequency Relative Frequency Relative Frequency ()
Cat 24
Dog 35
Fish 21
Rat 64
24/144
16.67
35/144
24.31
21/144
14.58
44.44
64/144
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Drawing Pie Chart

• Need to calculate angles
• 3600 altogether
• Use relative frequencies ( or fraction)
• Fractions may be more accurate!
• Cat 24/144 360 (or 16.67 of 360)
• 24 144 X 360 600

of
X
10
Similarly

• Dog 35/144 X 360 87.50
• Fish 21/144 X 360 52.50
• Rat 64/144 X 360 1600
• Should add up to 3600
• May not due to rounding
• (especially if using )

11
Relative Frequencies and Pie Charts

• Rel Freqs help draw and interpret Pie Charts
• Angle Rel Freq

X 3600
12

• Ex Favourite Day
• Fri 20 Sat 28 Sun 23 Mon 1
• Total 72
• Rel freq Fri
• Sat
• Sun
• Mon
• Angles Fri
• Sat
• Sun
• Mon

20/72
28/72
23/72
1/72
20/72 X 3600
1000
28/72 X 3600
1400
1150
50
13
Pie Chart
Zero
1000
14
Pie Charts
1000
1400
00
1400
15
Pie Charts
16
Pie Charts
Mon
Fri
Sun
Sat