Statistics P6 Help needed

[math]

it's easy.....
if the probability has been given to you and it is less then 0.5, you can't read it's z value from the table......
Let x be the probability which is less then 0.5...
what we have to do is to minus the probability from 1(i.e 1-x)....
this calculated probability is obviously greater then 0.5....
Now read the z value for this calculated probability......
Now all you have to do is to include a negative sign in your z value......
Let
P(X<x)=0.25 (which is less then 0.5 )
P(X>x)=1-0.25
=0.75
From the table
z=0.674 for 0.75
z=-0.674 for 0.25

Hope you understand it.....and best of luck for your exams.....

thanks

 

[Adorkableme]

i don't understand when to choose the negative value of z.

same here can anyone plzz help

the negative value is chosen when z> something
the table only gives values for z being less then a particular value so for z grater then any value u will have to subtract it from one and it also becomes negative.

 

[Iadmireblue]

http://www.xtremepapers.com/papers/...S Level/Mathematics (9709)/9709_w11_qp_61.pdf

question 5 part (i) i don't understand why fi z=0.97 and not 0.94
please help

 

[usmiunique]

i wanted to know when to take the mean of the data when calculating the quartiles.​

for eg. in M/J/2010 paper 61 stats,​

in question 2, we get the following steam-and-leaf diagram.​

0|2 5 6 8 8 (5)​

1|2 4 6 7 7 9 (6)​

2|1 2 3 3 3 5 6 7 (8)​

3|1 5 (2)​

now in calculating the median, we will divide the total number of data by 2 which in this case is​

21/2=10.5 so, which value will we take? 10 th value or 11thvalue or the mean of the 10th and 11th value.​

also in calculating the lower quartile, we get 21/4=5.25 here also, do we take the 5th value or the 6th value or the mean of the 5t and 6th value?​

again in calculating the upper quartile, we get 21*0.75=15.75 here again do we take the 15th value or the 16th value or the mean of the 15th and 16th value?​

sometimes in the mark scheme i have seen them taking the mean and sometimes the value immediately next to it.. im confused as to what should i do?​

WILL appreciate any help!​

 

[Iadmireblue]

i wanted to know when to take the mean of the data when calculating the quartiles.​

for eg. in M/J/2010 paper 61 stats,​

in question 2, we get the following steam-and-leaf diagram.​

0|2 5 6 8 8 (5)​

1|2 4 6 7 7 9 (6)​

2|1 2 3 3 3 5 6 7 (8)​

3|1 5 (2)​

now in calculating the median, we will divide the total number of data by 2 which in this case is​

21/2=10.5 so, which value will we take? 10 th value or 11thvalue or the mean of the 10th and 11th value.​

also in calculating the lower quartile, we get 21/4=5.25 here also, do we take the 5th value or the 6th value or the mean of the 5t and 6th value?​

again in calculating the upper quartile, we get 21*0.75=15.75 here again do we take the 15th value or the 16th value or the mean of the 15th and 16th value?​

sometimes in the mark scheme i have seen them taking the mean and sometimes the value immediately next to it.. im confused as to what should i do?​

WILL appreciate any help!​

you take the 11th value,what ever decimal answer you get you always take the next whole number,even if it's 3.001 you take it as the 4th number

 

[sadman sakif]

can anyone please suggest what to do for the last 6 hrs as i am really weak with distributions !!!!!!!!!! please help ! i need to get above 35 tomorrow!!!

 

[usmiunique]

you take the 11th value,what ever decimal answer you get you always take the next whole number,even if it's 3.001 you take it as the 4th number

but in the mark scheme, they have taken the mean of 5th and 6th for the LQ. and for the UQ, they have taken the mean of the 16th and 17th value!

 

[Knight]

i wanted to know when to take the mean of the data when calculating the quartiles.​

for eg. in M/J/2010 paper 61 stats,​

in question 2, we get the following steam-and-leaf diagram.​

0|2 5 6 8 8 (5)​

1|2 4 6 7 7 9 (6)​

2|1 2 3 3 3 5 6 7 (8)​

3|1 5 (2)​

now in calculating the median, we will divide the total number of data by 2 which in this case is​

21/2=10.5 so, which value will we take? 10 th value or 11thvalue or the mean of the 10th and 11th value.​

also in calculating the lower quartile, we get 21/4=5.25 here also, do we take the 5th value or the 6th value or the mean of the 5t and 6th value?​

again in calculating the upper quartile, we get 21*0.75=15.75 here again do we take the 15th value or the 16th value or the mean of the 15th and 16th value?​

sometimes in the mark scheme i have seen them taking the mean and sometimes the value immediately next to it.. im confused as to what should i do?​

WILL appreciate any help!​

If the total number of data is odd then for the median, the value is (n+1)/2 i.e in this case (21+1)/2=11th value
For L.Q (21+1)/4=5.5 for this you take the mean of 5th and 6th
For U.Q (21+1)*3/4=16.5 for this you take the mean of 16th and 17th value
Hope you understand it....

For n being odd number
L.Q=(n+1)/4
Median=(n+1)/2
U.Q=(n+1)*3/4

For n being even number
L.Q=n/4
Median=n/2
U.Q=(n*3)/4

Where n=total number of data

 

[usmiunique]

thanks a LOT!

 

[azambezi]

erm how do you determine standard variation on a cumulative graph?

 

[sea_princess]

erm how do you determine standard variation on a cumulative graph?

u don't , u make a table using values from the graph , then calculate standard deviation

 

[Jaf]

erm how do you determine standard variation on a cumulative graph?

I don't think it would be possible for you to find the standard deviation if you only have the cumulative graph with you, without any actual values. (if they have crosses plotted on the graph, those would be your values). If you do have the values, find the frequencies. Then find the mean. And finally, find the standard deviation.
If you gave us a sample question it would be easier for your to understand.

 

[Knight]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w11_qp_62.pdf

In question 4(iv) shouldn't we be first finding out our class boundaries? The mark scheme directly used the values in the table for the histogram.
According to me the class boundaries should be:
-0.5≤x<19.5 19.5≤x<29.5 29.5≤x<39.5 39.5≤x<44.5 44.5≤x<49.5 49.5≤x<59.5 59.5≤x<69.5

The mark scheme specifically mentions a mark for 'correct bar widths starting at 20'.

Help?

In Q4;(iv) theweight is in grams which can take any value between 20 and 19 not only 20 or 19,so you don't need to find the class boundaries

In M/J/11 qp 63 Q3;(iii) mid points have to be worked out which are calculated by the method shown in the image.........
Hope you understand it..............

 

[Jaf]

In Q4;(iv) theweight is in grams which can take any value between 20 and 19 not only 20 or 19,so you don't need to find the class boundaries

So? I think I faintly get you point, but still I'm attaching a picture of an example from the Steve Dobbs S1 book which has the masses given and yet they still use class boundaries (why?):

In M/J/11 qp 63 Q3;(iii) mid points have to be worked out which are calculated by the method shown in the image.........

Did you, or did you not use class boundaries here? If not, why not?

Thanks!!

 

[Knight]

So? I think I faintly get you point, but still I'm attaching a picture of an example from the Steve Dobbs S1 book which has the masses given and yet they still use class boundaries (why?):
View attachment 10586



Did you, or did you not use class boundaries here? If not, why not?

Thanks!!

use these values of class widths to draw the histogram

and in M/J/11 qp 63 Q3;(iii) mid-points are not changed by either using or not using the class boundaries.......

 

[Jaf]

View attachment 10597
use these values of class widths to draw the histogram

and in M/J/11 qp 63 Q3;(iii) mid-points are not changed by either using or not using the class boundaries.......

Kind sire, I understand what we have to do in order to get congruent answers as the mark scheme. I don't get why we have to do it? Is there a rule when we have to find the boundaries?

Thanks again.

 

[lavanyamane]

Kind sire, I understand what we have to do in order to get congruent answers as the mark scheme. I don't get why we have to do it? Is there a rule when we have to find the boundaries?

Thanks again.

Exact. Same. Problem. !!

 

[Knight]

Exact. Same. Problem. !!

Kind sire, I understand what we have to do in order to get congruent answers as the mark scheme. I don't get why we have to do it? Is there a rule when we have to find the boundaries?

Thanks again.

Here is a tutorial on histograms............Hope you like it...

 

[Jaf]

*sigh*

Thanks.

 

[gadagada]

can anyone plzz help me with this

Which year is this question from?