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Feb/Mar 2023 p52 q1
2444
Each year the total number of hours, \(x\), of sunshine in Kintoo is recorded during the month of June. The results for the last 60 years are summarised in the table.
\(x\)
30 \(\leq x <\) 60
60 \(\leq x <\) 90
90 \(\leq x <\) 110
110 \(\leq x <\) 140
140 \(\leq x <\) 180
180 \(\leq x <\) 240
Number of years
4
8
14
25
7
2
Calculate an estimate for the mean number of hours of sunshine in Kintoo during June over the last 60 years.
Solution
To estimate the mean number of hours of sunshine, we first find the midpoints of each class interval:
For \(30 \leq x < 60\), midpoint = 45
For \(60 \leq x < 90\), midpoint = 75
For \(90 \leq x < 110\), midpoint = 100
For \(110 \leq x < 140\), midpoint = 125
For \(140 \leq x < 180\), midpoint = 160
For \(180 \leq x < 240\), midpoint = 210
Next, we calculate the weighted sum of the midpoints: