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Estimating the median

is there a way for someone to explain Estimating the median, to me like im five (like the sub reddit ). or give me a helpful video

===Moved to Maths===
(edited 7 years ago)
Original post by omichael
is there a way for someone to explain Estimating the median, to me like im five (like the sub reddit ). or give me a helpful video


Is this for grouped frequency tables?
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omichael
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Original post by SeanFM
Is this for grouped frequency tables?


Yep s1
Original post by omichael
Yep s1


https://www.mathsisfun.com/data/frequency-grouped-mean-median-mode.html

Attempt #3 to post this.. TSR is playing up which is a bit annoying.. has deleted my post twice now.

The link above is useful but let's give you another example... this assumes that you know how to find the class with the median in it already.

Let's say you have grouped frequencies of

0-10 has a frequency of 10
11-20 has a frequency of 5
21-30 has some frequency which doesn't particularly matter, apart from finding the median number

Now let's say the median is the 14th number, so it's in the 11-20 class.

When we're estimating the median, essentially (from the formula given in the link above for it) we're assuming that the numbers are evenly distributed across the class. In this case, the class width for the median is 10 (20.5 - 10.5) - don't forget the extra 0.5s!) and the frequency is 5, so the gap between each data point would be 2 (class widh / frequency = 10/5) if it were evenly distributed, so the estimates would be that the actual points in the class are 12.5, 14.5, 16.5, 18.5 and 20.5 (you don't include the first one which would be 10.5, the formula will never give you the lower limit because it would just be the same as the upper limit from the previous class which is the 10th value of 0-10. ).

And we know that we want the 4th value so it will be 18.5.

Of course the 12.5, 14.5 etc are just estimates hence this is an estimate of the mean. It could perfectly be possible that all the data points in the 11-20 class were 12,12,12,12,12 or 19,19,19,19,19 in extreme cases but it's most likely (I think) that the median number will be 18.5 if it's the 4th number in the class, 16.5 if it's the 3rd etc.

Note that this is what effectively the formula is doing (which after enough looking at it and considering examples you will understand easily), but you will need to use the formula to actually get the number, so in this case

L= 10.5,

n = 14,
B = 10,
G = 5,
w= 10 and so putting it in the formula gives 10.5 + (4/5)*10 = 10.5 + 8 = 18.5.


I know that may be confusing at first but let me know if you have any questions.
(edited 7 years ago)
interpolation?
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omichael
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Original post by sulaimanali
interpolation?


Yep

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