Statistics 1 Revision Notes - Mr Barton Maths

To find Q 2 , n = 202
⇒
= 101 do not change it
class
boundaries
cumulative
frequencies
10 Q 2 20
63 101 117
From the diagram
⇒ Q 2 = 10 + 10 ×
= 17⋅037…= 17⋅0 to 3 S.F.
Similarly for Q 3 , = 151⋅5, so Q 3 lies in the interval (20, 30)
⇒
.
⇒
Q 3 = 20 + 10 × .
= 27⋅0408… = 27⋅0 to 3 S.F.
Grouped frequency tables, discrete data
The discrete data in grouped frequency tables is treated as continuous.
1. Change the class boundaries to the 4 , 9 etc.
2. Proceed as for grouped frequency tables for continuous data.
class class
cumulative
frequency
interval boundaries
frequency
0 – 4 0 to 4 ½ 25 25
5 – 9 4 ½ to 9 ½ 32 57
10 – 19 9 ½ to 19 ½ 51 108
20 – 29 19 ½ to 29 ½ 47 155
30 – 59 29 ½ to 59 ½ 20 175
60 –99 59 ½ to 99 ½ 8 183
To find Q 1 , n = 183 ⇒ = 45⋅75
class
boundaries
4⋅5 Q 1 9⋅5
cumulative
frequencies
25 45⋅75 57
From the diagram
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16 14/04/2013 Statistics 1 SDB