The number ot telephone calls received at an exchange per interval for 250 successive one-minute intervals are given in the following frequency table:
No. of calls (x) : 0 1 2 3 4 5 6
No. of intervals (f) : 15 24 19 46 54 43 39
Compute the mean number of calls per interval.

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Solution

Mean = $fraction numerator begin display style stack sum f subscript i x subscript i with i equals 1 below end style over denominator N end fraction$ = $fraction numerator 0 cross times 15 thin space plus space 1 cross times 24 plus 2 cross times 19 plus 3 cross times 46 plus 4 cross times 54 plus 5 cross times 43 plus 6 cross times 39 over denominator 15 plus 24 plus 19 plus 46 plus 54 plus 43 plus 39 end fraction$

Mean =

The mean number of calls per interval is 3.604

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Similar questions

No. of calls (x):	0	1	2	3	4	5	6
No. of intervals (f):	15	24	29	49	54	43	39

250

No. of calls ( $x$ )	$0$	$1$	$2$	$3$	$4$	$5$	$6$
No. of intervals ( $f$ )	$15$	$24$	$29$	$46$	$54$	$43$	$39$

The number of telephone calls received at an exchange in 245 successive one-minute intervals are shown in the following frequency distribution :

$\begin{matrix} Number of calls & 0 & 1 & 2 & 3 & 4 & 5 & 6 & 7 Frequency & 14 & 21 & 25 & 43 & 51 & 40 & 39 & 12 \end{matrix}$

Compute the mean deviation about median.

Number of calls	0	1	2	3	4	5	6	7
Frequency	14	21	25	43	51	40	39	12

Number of calls	0	1	2	3	4	5	6	7
Frequency	14	21	25	43	51	40	39	12

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