Find the weighted mean of 15, 20 and 25 with weights 2, 3 and 5, respectively.
21.5
Weighted mean = \(\frac{\sum w_i x_i}{\sum w_i}\), where each value is multiplied by its weight.
\(\sum w_i x_i\) = 15 × 2 + 20 × 3 + 25 × 5 = 30 + 60 + 125 = 215, and \(\sum w_i\) = 2 + 3 + 5 = 10.
Weighted mean = \(\frac{215}{10} = 21.5\).
Check: the deviations from 21.5 weighted by 2, 3 and 5 are 2 × (–6.5) + 3 × (–1.5) + 5 × 3.5 = –13 – 4.5 + 17.5 = 0, as required for a mean.
Hence, 21.5.
Similar Questions
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Important Questions from Measures of Central Tendency
A random sample of 20 people is classified in the following table according to their ages:
Age
Frequency
15 – 25
2
25 – 35
4
35 – 45
6
45 – 55
5
55 - 65
3
What is the mean age of this group of people?
The median of the following observations 46, 64, 87, 41, 58, 77, 35, 90, 55, 92, 33 is 58. If 92 is replaced by 99 and 41 by 43 in the above data. The new median is:
If the difference of mode and median is 36, then the difference of median and mean is:
In a Mathematics test 15 students scored 80 marks, 20 students scored 75 marks, 28 students scored 65 marks and 25 students scored 60 marks, mode of the score is:
If the mode of the scores 10, 12, 13, 15, 15, 13, 12, 10, x is 15, then what is the value of x?
