IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => IGCSE/ GCSE => Math => Topic started by: vids on May 18, 2009, 06:52:07 am
-
maths p4
nov 03 q 8(b)
-
histograms???? ???
-
I really would like to help but am not sure ::)
I think we have to first make the table:
less than 10
less than 15
less than 20
...............................
sry for not helping the way you need :-\
-
Find frquency densities by dividing frequencies by the lengths in the intervals
Length Frequency density
0-10 12/10=1.2
10-15 32/5=6.4
15-20 28/5=5.6
20-25 24/5=4.8
25-40 24/15=1.6
Now draw bars, Length on the x axis and frequency density on the y axis. Make sure you get even scales.
-
RANGE :0<m<=10 10<M<=15 15<M<=20 20<M<=25 25<M<=40
WIDTH : 10 5 5 5 15
FREQU.: 12 32 28 24 25
THE SCALE 2cm - 5 kg
1cm - 2.5kg
the standard width taken is 2.5
now...
---------------------RULE------------------------------------------------------------------
if class width = n * standars width, then the height of the rectangle = frequency/n
---------------------------------------------------------------------------------------------
for the 1st.) 10 = n * 2.5 ...therefore n = 4 => height = 12/4 = 3
2nd.) 5 = n * 2.5....therefore n = 2 => height = 32/3 = 16
3rd.) 5 = n * 2.5....therefore n = 2 => height = 28/2 = 14
4th.) 5 = n * 2.5....therefore n = 2 => height = 24/2 = 12
5th.) 15 = n * 2.5....therefore n = 6 =>height = 24/6 = 4
v have been taught this method
is this correct.
plz chk the markscheme
i don't have it
-
No the height is the freoency dividing by the length of the interval so for the first one the height is 12/10=1.2
-
The height is called the frequency density for histograms.
-
ohh..
thanks a lot :)
By the way...wat does the markscheme say..
can u plz upload it
i don't have it
-
www.freeexampapers.com
?
-
ohh..yaa..i'll try in that...
-
The ms is there but is in 1 file for all the papers.
-
Hey sweetsh your avater is really good!
-
Haha! Nice idea right?
-
i got the markscheme ..
it says..
1 mark for - horizontal scale 2cm = 5cm
1 mark for - k =1
5 marks for the heights - 3k, 16k, 14k, 12k, 4k
??
-
Where did you get it? I might get one.
-
Then it is the scale times all the frequency densities by 2.5 to get the height.
-
ohh..
k..
tks
:)
-
its quite simple. First make sure that the data is continuous which in your question is i.e when ir say 10<x<15, the next one shud also start with 15 i.e 15<x<25. Then make sure that the class width is equal i.e 15-10 or watever. If class width is equal u plot the frequency and if not then u plot the frequency density which is
Frequency Density=Frequency divided by class width
-
u gotta multiply it with th standard width too...
i.e 2.5
-
ok.