S2 Cumulative freq

http://www.examsolutions.net/a-level-maths-papers/Edexcel/Statistics/Statistics-S2/2012-June/paper.php

For question 7B can someone explain how I would do the '1/5' part ?

the method I use is to integrate the first function =0 and sub in the lower limit. Next I would integrate the last function =1, and sub in the larger limit.

Reply 1

Kevin De Bruyne

21

Original post by imran_

http://www.examsolutions.net/a-level-maths-papers/Edexcel/Statistics/Statistics-S2/2012-June/paper.php

For question 7B can someone explain how I would do the '1/5' part ?

the method I use is to integrate the first function =0 and sub in the lower limit. Next I would integrate the last function =1, and sub in the larger limit.

I think I kind of see what you said there but not 100% sure what it is or what it achieves - would you mind clarifying please? :h:

Reply 2

imran_

OP

2

Original post by SeanFM

I think I kind of see what you said there but not 100% sure what it is or what it achieves - would you mind clarifying please? :h:

For example if we're given f(x)=1/5 with limits 1<x<4

to find F(X) i would do integrate it and make it =0 and sub in the lowest limit.

1/5x+c=0 (integral)

sub in 1 (lowest value) and solve for C

c= -1/5

Reply 3

Kevin De Bruyne

21

Original post by imran_

For example if we're given f(x)=1/5 with limits 1<x<4

to find F(X) i would do integrate it and make it =0 and sub in the lowest limit.

1/5x+c=0 (integral)

sub in 1 (lowest value) and solve for C

c= -1/5

Ohh, I see what you mean, and it's kind of like the opposite... interesting method, but you could do it a bit better.. (I think)

So for x^2/45, you integrate between x and the lower limit to find the CDF for that region.

The middle bit, you also integrate between x and the lower region (which basically is finding F(x) - f(3), so it only takes the probabilities in that region, so to find the CDF (remember that F(x) means the probability of f being x or less) you need to add F(upper limit of previous region), which makes sense if you think about it, because you're basically combining the probability of a value being between 3 and x, plus the probability of the value being less than 3, which adds together to give probability of X being less than x. In notation, that's

P(3 < X \leq x) + P( X \leq 3) = P( X \leq x)

.

And you can use a similar logic for the third part (and 'joining it' on to to the second part, which already has the first part joined.

S2 Cumulative freq

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you