Err.. Need help. - Histograms [maths]

[Muho]

Histograms are bugging me. I just want to know the general rule for this. They ask us not to draw a histogram, and they give us a height of one bar, and then we have to find the rest of the heights for the other classes. Please someone help if you have the faintest idea about this. xD

it's not that urgent. I have enough time, hopefully someone will answer before the exam or something. ^^

[astarmathsandphysics]

Histograms are bugging me. I just want to know the general rule for this. They ask us not to draw a histogram, and they give us a height of one bar, and then we have to find the rest of the heights for the other classes. Please someone help if you have the faintest idea about this. xD

it's not that urgent. I have enough time, hopefully someone will answer before the exam or something. ^^

The height is the frequency density so do the frequency density for all the classes and use the one they give you to get a scale on the frequency density axis.

[orbit]

i guess the height is (frequency/class width)

[IG4ever]

to draw the histogram u must find the frequency density (F.D)
F.D=frequency/width
example:
|mass       |5-|8-|10-15|
|frequency| 4 |3 | 7     |
  the table shows the mass of 14 student..... draw the histogram.

width= difference between each 2 masses
|mass       | 5-     | 8-     |10-15|
|frequency| 4      | 3       | 7     |
|F.D         | 4/3    |3 /2    |7/5    |

NB. Height=F.D    ///    Area = frequency
hope u liked it

[Shogun]

u see the hight is actually the frequency density.
and to get frequency density = frequency/class width
they will give u one hight probably to find one of the frquency or class width
they will give you ranges which apparently are above the frequency. and from there u find the class width by just minusing the big number minus the small number in a range then apply the formula
                                 frequency/class width
then u get the frquency density which will lie on your (y axis) the ranges lie on the (x axis) then draw the bars respectively to the appropriate frequency density and the ranges.

[Ghost Of Highbury]

any past paper question which asks to find the height of other rectangles??

[Muho]

any past paper question which asks to find the height of other rectangles??

Yeah, Oct/Nov 2008
Q6 b (ii)

[Ghost Of Highbury]

okk..heres how u do it..
---------------RULE---------------------------------------------------
if class width = n * standard width, then, height = frequency/n
--------------------------------------------------------------------------
first lets find the standard width...the  height given = 11.5, its frequency is 115
therefore 11.5 = 115/n...=> n = 10
class width = 10 * standard width
2              =  10 * standard width
therefore standard width = 0.2
-----------------------------------------------------
now use this formula with standard width 0.2 to calculate the heights..
height = fequency * (standard width/classwidth)
1st - h = 35 * 0.2/10 = 0.7
2nd - 11.5 (given)
3rd - h = 26 * 0.2/2 = 2.6
4th - h = 24 * 0.2/6 = 0.8
----------
chk the markscheme for verification
good luck
byee

[Muho]

Cheers, helped me this time. xD thanks for explaining guys. come closer paper 4, come closer *drools*

[Ghost Of Highbury]

happy to help u!!