Question

If total frequencies of three series are 50,60 and 90 and their means are 12, 15 and 20 respectively, then composite mean is
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Answer 1

Given:-

Frequencies of three series are 50, 60 and 90  and their means are 12, 15 and 20 respectively.

To Find:-

Composite mean of the set

Solution:-

For a single series, mean is calculated by the simple method but for more than one series, mean is calculated for each series separately and then the results are combined to obtain a composite mean.

Let the frequencies be f₁, f₂ and f₃ and their means be x₁, x₂ and x₃ respectively.

Formula to calculate composite mean:

$\frac{f1.x1 + f2.x2 + f3.x3}{f1 +f2+ f3}$

⇒$\frac{(50.12)+ (60.15) +(90.20)}{50+60+90}$

⇒$\frac{3300}{200}$

⇒16.5

Hence, the composite mean o the given series is 16.5