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# formula for a median for grouped data

what is the formula to find a median of grouped data

Median = L + I *(N/2 - F)/f

where:

L = lower limit of the interval containing the median
I = width of the interval containing the median
N = total number of respondents
F = cumulative frequency corresponding to the lower limit
f = number of cases in the interval containing the median

Hope this is what you were looking for.

The median is simply the middle number of a group of data.

For instance if you had 11 numbers 1,2,3,4,5,6,7,8,9,10,11; The median would be 6.  There are an equal number of data points above and below it.  1,2,3,4,5 [6] 7,8,9,10,11

If there were and even number of numbers, 1,2,3,4,5,6,7,8,9,10; then you would take the average of the middle two numbers:  (5+6)/2 = 5 1/2.  1,2,3,4,5 [5 1/2] 6,7,8,9,10.

If you are asking about an Excel formula, you can put the list of numbers in a column and then type in a cell "=MEDIAN(A1:A<to whatever the end of you list is>).  This will calculate it automatically.

Have fun with your statistics!  A great subject!!!

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