The number of telephone calls received at an exchange per interval for 250 successive one-minute intervals are given in the following frequency table:
Question:
The number of telephone calls received at an exchange per interval for 250 successive one-minute intervals are given in the following frequency table:
Compute the mean number of calls per intervals.
Solution:
Let the assume mean be $A=3$.
We know that mean, $\bar{X}=A+\frac{1}{N} \sum_{i=1}^{n} f_{i} d_{i}$
Here, we have $N=\sum f_{i}=250, \sum f_{i} d_{i}=135$ and $A=3$.
Putting the values in the formula, we get
$\bar{X}=A+\frac{1}{N} \sum_{i=1}^{n} f_{i} d_{i}$
$=3+\frac{1}{250} \times 135$
$=3+0.54$
$=3.54$
Hence, the mean number of calls per interval is 3.54.
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