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# A2 Statistics watch

1. f(x) = x/8 for 0 <= x <= 4
= 0 otherwise

find median value of x
2. (Original post by uzer)
f(x) = x/8 for 0 <= x <= 4
= 0 otherwise

find median value of x
Find .
Then use the fact that .
3. f(x) is given.. i have done that and then i intergrated a got x^2/16 and then my asnwr is wrong
4. (Original post by uzer)
f(x) is given.. i have done that and then i intergrated a got x^2/16 and then my asnwr is wrong
*I, I, integrated, and, answer

Yes, that is correct.
So
5. (Original post by morgan8002)
*I, I, integrated, and, answer

Yes, that is correct.
So
so then the answer comes out as 4, but my book says 2.8
6. (Original post by uzer)
so then the answer comes out as 4, but my book says 2.8
Show the rest of your workings, you are correct so far and I have (3sf)
7. m2 = 0.5 times 16

m2 = 8

square root both sides m =4
8. (Original post by uzer)
m2 = 0.5 times 16

m2 = 8

square root both sides m =4

(3sf)
9. yes thank you its late at night so
10. (Original post by uzer)
yes thank you its late at night so
You're welcome. I thought that might be the case. Maybe in future use a calculator if you're tired.
11. hi please differentiate

2x/9 (3-x)

for 0<=x<=3

i solved f'(x) for zero and got 0.5.

12. (Original post by uzer)

2x/9 (3-x)

for 0<=x<=3

i solved f'(x) for zero and got 0.5.

Are you trying to find f'(0) or the value of x for f'(x) = 0

at
13. (Original post by uzer)

2x/9 (3-x)

for 0<=x<=3

i solved f'(x) for zero and got 0.5.

f(x) = a/x for 1<=x<=2
0 otherwise

find median value of x. i have differentiated but am failing to get the correct answer
14. (Original post by uzer)
f(x) = a/x for 1<=x<=2
0 otherwise

find median value of x. i have differentiated but am failing to get the correct answer
Show your working and I can tell you where you went wrong.
15. f'(X) = -2ax^-2 =0
now i am stuck
16. (Original post by uzer)
f'(X) = -2ax^-2 =0
now i am stuck
You integrate to find the median
It should be

As a side note, the general convention is the pmf is denoted by f(x) and the cdf is denoted by F(x)
17. (Original post by morgan8002)
You integrate to find the median
It should be

As a side note, the general convention is the pmf is denoted by f(x) and the cdf is denoted by F(x)
and then i times by x is that correct
so its x a ln(x) = 0.5
18. (Original post by uzer)
and then i times by x is that correct
so its x a ln(x) = 0.5
No I think you're confusing the median with mean.

To find the mean, you do

To find the median, you find F(x), where , then use

For each of these, the infinities just mean the limits of where the function is defined, for your question it will be 1 and 2.

So you should do
19. 2^x + 1 divided by 2^x -1 = 5

i tried cross multiplying but no luck
20. (Original post by uzer)
2^x + 1 divided by 2^x -1 = 5

i tried cross multiplying but no luck

And carry on from there

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