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Question

# Thirty women were examined in a hospital by a doctor and the number of heart beats per minute recorded and summarised as follows. Find the mean heat beats per minute for these women, choosing a suitable method. Number of heart beats per minute: 65-58 68-71 71-74 74-77 77-80 80-83 83-86 Number of women: 2 4 3 8 7 4 2

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Solution

## Let the assumed mean be A = 75.5 and h = 3. No. of Heart Beats per Min: Mid Value $\left({x}_{i}\right)$ No. of Women $\left({f}_{i}\right)$: ${d}_{i}={x}_{i}-A$ ${u}_{i}=\frac{1}{h}×{d}_{i}$ ${f}_{i}{u}_{i}$ 65-68 66.5 2 $-$9 $-$3 $-$6 68-71 69.5 4 $-$6 $-$2 $-$8 71-74 72.5 3 $-$3 $-$1 $-$3 74-77 75.5 = A 8 0 0 0 77-80 78.5 7 3 1 7 80-83 81.5 4 6 2 8 83-86 84.5 2 9 3 6 $\sum {f}_{i}=30$ $\sum {f}_{i}{u}_{i}=4$ We know that mean, Now, we have. Putting the values in the above formula, we have Hence, the mean heart beats per minute for women is 75.9.

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