For example I have this set of grouped data Class: 1-5 | 5-10 | 10-15 | 15-20 Frequency: 2 | 3 | 3 | 2

Since n = 2 + 3 + 3 + 2 = 10 which is even Then the median should be the average of the 5th and 6th values. However, the 5th and 6th values lie in different classes. Where would the median lie? How am I supposed to calculate the estimated median with the following formula:

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If the median is between two classes, isn't your work already done? In your case, the median is 10.5 - the midpoint of the interval between the two classes - and you don't need the formula.

  • $\begingroup$ But suppose the OP's fifth value is 5 and the sixth 10 which as far as I can tell is consistent with the tabulation? $\endgroup$
    – mdewey
    Jun 25 '17 at 16:52
  • $\begingroup$ Well, really, all the values between the two classes are medians. Half the values above and half below. Since the data are grouped, we have no basis for preferring anything other than the midpoint. $\endgroup$
    – Peter Flom
    Jun 25 '17 at 21:03

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