The Student Room Group

median from histograms?

i've done this once before in class but i can't remember how its done...it's something to do with fractions/ratios in the frequency table i think :confused:

anyone like to help?

plus, do we actually need to know this for gcse? i've only ever seen it in the textbook at school but not in any gcse revison guide/revision site

i guess it would be nice to know any how

so guys how is it done ? :biggrin:
Reply 1
To find the median, you find the number that is in the middle.

Just add the frequency of the numbers together (not the actual number) and divide by 2 to find where the middle number should be. Alternatively, you could list the numbers and find the middle one
Reply 2
find the cumulative freq then divide by 2.
Reply 3
thx guys but i was asking if you had to estimate the median from a histogram if you weren't given the individual values...i know how to do it now though...but thanks for you help anyway :biggrin:
Reply 4
this is not on module 5
Reply 5
i'm doing edexcel linear :biggrin: and it's in the textbook for it and i've only ever done it on one practice solomon or churchill past paper
So how do you work it out if no values are given
Reply 7
work out areas of bars.
add them up then find the middle value then see what bar that is I suppose.
Ah right thanks :smile:
How do you do it ?
I have a question :

Time (m) Frequency FD CW
0<m<20 20 1 20
20<m<30 30 3 10
30<m<40 45 4.5 10
40<m<60 60 3 20
60<m<100 48 1.2 40

1) Work out an estimate for the median time : ................ minutes

CAN SOMEONE PLEASE HELP ME, AND SHOW ME HOW TO WORK IT OUT
Step by Step (The f column adds up to 203. If you divide that by 2 you get 101.5 ~ then you work out the class it is in ???)

THE ANSWER IS : 41 -43 minutes
I JUST NEED TO KNOW HOW TO WORK IT OUT ... my gcse is tomorrow :O

Thanks
Reply 10
Frequency Density = Frequency / Class width
so Frequency = Frequency density X class width

Once you've found frequency...

Median = n/2 (where n is total frequency)
Once you've found median add up to frequencies until you've got up to your median and look at which class interval it lies in.
Reply 11
Would you have to list the class it lies in?
Reply 12
How!!!!! I know you're not doing GCSE anymore but now I have the same question!!!!
Reply 13
the area of the histogram is the frequency, so you just figure out the frequency of each bar of the histogram, divide by 2 then find the histogram bar that has that frequency.
Hello I was just wondering what happens if i have two medians (middle values) in my histogram ???please help! I have an assignment about it and am completely lostHelp needed ASAP if able Thanks a billion :smile:
Reply 15
Original post by Horselover29
Hello I was just wondering what happens if i have two medians (middle values) in my histogram ???please help! I have an assignment about it and am completely lostHelp needed ASAP if able Thanks a billion :smile:

Hi, this is a very old thread so I am going to close it. Instead please start a new thread with your question indicating what level you are at e.g. GCSE/A Level. It would also be very useful if you post an example question with your attempt.

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