During a medical check - up, the number of heart beats per minute of 30 patients were recorded and Summarized as follows:


Number of heart - beats per minute



65 - 68



68 - 71



71 - 74



74 - 77



77 - 80



80 - 83



83 - 86



Number of patients



2



4



3



8



7



4



2



Find the mean heartbeats per minute for these patients, choosing a suitable method.

We will find the mean heartbeats per minute by direct method.


CLASS



MID - POINT(xi)



FREQUENCY(fi)



fixi



65 - 68



66.5



2



133



68 - 71



69.5



4



278



71 - 74



72.5



3



217.5



74 - 77



75.5



8



604



77 - 80



78.5



7



549.5



80 - 83



81.5



4



326



83 - 86



84.5



2



169



TOTAL




30



2277



We have got


Σfi = 30 & Σfixi = 2277


∵ mean is given by



⇒


⇒


Thus, mean is 75.9 heartbeats per minute.


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