Question

Continuous Random variable problem

Answer 1

\[\int\limits_{1}^{5} f(x) dx=1\]

Answer 2

so \[\int\limits_{1}^{5} c. (x-1).(x-5)=1\]

Answer 3

this gives c=-3/32

Answer 4

so we are done with the first question @Andresfon12

Answer 5

the first question got mess up skip and putting a new question

Answer 6

the second question ?? the density function is not given

Answer 7

c=-3/32

Answer 8

yes thats what we got

Answer 9

the density function is (3;x)

Answer 10

is the second question a continuation of the first?

Answer 11

yes

Answer 12

What does your book mean by DF(3;X)?

Answer 13

it mean that (x<=3) and (x>3)

Answer 14

here example from the notes

http://assets.openstudy.com/updates/attachments/563d6341e4b0dcbad1ef0b4c-andresfon12-1446863856310-notes.png

Answer 15

see third part you need to compute
\[\int\limits_{1}^{5} (-3/32) x. (x-1)(x-5) \]

Answer 16

which is 3 after computation

Answer 17

so E(X)=3

Answer 18

ok

Answer 19

part 2 is tricky?

Answer 20

Not tricky... My book has a different expression of it, so I am not able to figure it out what it means. If I know the meaning, i can solve easily.. does it mean P(X<=3) ???

Answer 21

perhaps yes

Answer 22

If yes, then compute
\[\int\limits_{1}^{3} f(x) dx\]

Answer 23

k

Answer 24

and if it means P(X>3) then find
\[\int\limits_{3}^{5} f(x)dx\]

Answer 25

@Andresfon12 can you give me a picture of the theory portion? I checked the web and still didnot find anything which imply DF(3;X) Thanks

Answer 26

http://assets.openstudy.com/updates/attachments/563d6341e4b0dcbad1ef0b4c-andresfon12-1446863857321-notes1.png

Answer 27

http://assets.openstudy.com/updates/attachments/563d6341e4b0dcbad1ef0b4c-andresfon12-1446863857103-notes2.png

Answer 28

@Andresfon12 your attachment dont give the expression DF(3;X)

Answer 29

this last part of the page http://assets.openstudy.com/updates/attachments/563d6341e4b0dcbad1ef0b4c-andresfon12-1446863856713-note4.png

Answer 30

no so easy to part 2 i see

Answer 31

then you post the solution

Answer 32

the solution said is 1/2 that where i'm stuck lol

Answer 33

@freckles

Answer 34

please help with the second part.

Answer 35

\[(-3)\frac{ 1 }{ 32 }(48)\] i don't know for sure perhaps im wrong

Answer 36

@freckles I dont know what DF(3;X) mean

Answer 37

so does
\[DF(3;X) \text{ the same as } DF_x(3)?\]

Answer 38

from your notes if that is so it lookes you just evaluate:
\[\int\limits_1^3 \frac{-3}{32}(x-1)(x-5) dx\]

Answer 39

im not sure but i think ist dfx (3)

Answer 40

i know that is X^3/3-6x+15

Answer 41

what?

Answer 42

where are you getting that from

Answer 43

@freckles then its same as P(X<=3) ?

Answer 44

i just combine the (x-1)(x-5)

Answer 45

\[x^2-6x+5\]

Answer 46

\[\int\limits_{}^{} \frac{ x^3 }{ 3 }-3x^2+5x\]

Answer 47

yes I'm correct to assume DF(3;x) is the same as DF_x(3)

Answer 48

you can drop the integral sign after integrating

Answer 49

ok

Answer 50

\[\int\limits\limits_1^3 \frac{-3}{32}(x-1)(x-5) dx =\frac{-3}{32}(\frac{x^3}{3}-3x^2+5x)|_1^3\]

Answer 51

and then the answer is 1/2

Answer 52

yes if I'm correct to assume DF(3;x) is the same as DF_x(3)*

Answer 53

I have no idea if those things are equivalent
and I'm just using what the notes say fro DF_x(2)
like here http://assets.openstudy.com/updates/attachments/563d6341e4b0dcbad1ef0b4c-andresfon12-1446863856310-notes.png

Answer 54

give back the same result \[\frac{ -3 }{ 32 }\frac{ -32 }{ 3}\]

Answer 55

that note are bit messy lol

Answer 56

how did you get -3/32*-32/3 ?

Answer 57

should be -3/32*-16/3

Answer 58

(27/3-27+15)-(1/3-3+5)

Answer 59

[(-3)-(25/3)] = -32/3

Answer 60

figuring out how u get -16/3

Answer 61

how did you calculate 1/3-3+5 to be 25/3?

Answer 62

-3+5 is 2
1/3+2 is not 25/3

Answer 63

1/3+2 is 7/3

Answer 64

you have -3-7/3

Answer 65

-9/3-7/3=-16/3

Answer 66

ya u are right mistype the symbol the positive instead of the negative

Answer 67

1/3+3+5, should be 1/3-3+5

Answer 68

you had 1/3-3+5 above

Answer 69

ya but on my calculate no on the post

Answer 70

oh ok

Answer 71

ya (-3/32)*-(-16/3)= 1/2

Answer 72

(-3/32)*(-16/3)=1/2*

Answer 73

yep

Answer 74

so if we have like df(2;x) that mean is \[\int\limits_{1}^{2}\]?

Answer 75

so that mean the df is the distribution function or the density function, to make clear ?

Answer 76

I don't know.... I just made an assumption going of your notes

Answer 77

ok

Answer 78

still don't know if DF(3;x) means DF_x(3)

Answer 79

the way your notes used DF_x(3) is the same as P(x <=3)

Answer 80

just the prof doesn't specify the df from what he wrote in the board

Answer 81

that make a bit clear

Answer 82

http://assets.openstudy.com/updates/attachments/563d6341e4b0dcbad1ef0b4c-andresfon12-1446863856310-notes.png

Answer 83

this is what you posted earlier

Answer 84

yep that what i posted

Answer 85

that DF_x(2) thing he found is the same as P(x <= 2)

Answer 86

ohh ok

Answer 87

but I don't your notes mention the notation of DF(2;x) anywhere
if it did it escaped my attention

Answer 88

that just a example he did on the board

Answer 89

just similar question but different numbers

Answer 90

i see now

Answer 91

oh so DF(x;3) does means DF_x(3)?

Answer 92

anyway thank you so much,
i will ask him about that