Question

Calculate the sample variance and sample standard deviation for the following frequency distribution of heart rates for a sample of American adults. If necessary, round to one more decimal place than the largest number of decimal places given in the data.

Heart Rates in Beats per Minute

Class	Frequency
61 - 66	10
67 - 72	6
73 - 78	14
79 - 84	5
85 - 90	14

Answer 1

Solution-:

We prepare the following table:

Class	Freq(fi)	Mid Pt. (xi)	fi*xi	fi*xi^2
61-66	10	63.5	635	40322.5
67-72	6	69.5	417	28981.5
73-78	14	75.5	1057	79803.5
79-84	5	81.5	407.5	33211.25
85-90	14	87.5	1225	107187.5
Total	49		3741.5	289506.3

From this table we get,

Sample mean,

and Sample variance,

Sample standard deviation,