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Statistics - "within" keyword

Say you had the following:

X = # of hours past midday
F(X) = x, 0 <= x < 24

If you wanted to calculate if the random variable would be within 3 hours would it be P(X < 3) or P(X <= 3)?
(edited 11 years ago)
Original post by JJMills
Say you had the following:

X = # of hours past midday
F(X) = x, 0 <= x < 24

If you wanted to calculate if the random variable would be within 3 hours would it be P(X < 3) or P(X <= 3)?


P(X<=3), IMO.

Edit Changed my mind.

Consider what within 1 hour means. Would F(x) by 0 or 1?
(edited 11 years ago)
Reply 2
Original post by ghostwalker
P(X<=3), IMO.

Edit Changed my mind.

Consider what within 1 hour means. Would F(x) by 0 or 1?


Within, to me, implies under 1 hour (i.e. < not <=).

Just wanted to check if I was correct :smile:
Reply 3
Original post by JJMills
Say you had the following:

X = # of hours past midday
F(X) = x, 0 <= x < 24

If you wanted to calculate if the random variable would be within 3 hours would it be P(X < 3) or P(X <= 3)?


Haha i see what is going on here. :smile:


Posted from TSR Mobile
Original post by JJMills
Within, to me, implies under 1 hour (i.e. < not <=).

Just wanted to check if I was correct :smile:


< was my initial thought.

It looks to be a discrete uniform distribution.

Then I though about what the r.v. represented, or might represent, since there's no info there, and decided <=. But could be either I suspect.

Is there any background information?
Reply 5
Im confused :/ generally within 1 hour means including 1 hour?
Reply 6
Original post by ghostwalker
< was my initial thought.

It looks to be a discrete uniform distribution.

Then I though about what the r.v. represented, or might represent, since there's no info there, and decided <=. But could be either I suspect.

Is there any background information?


If it said continuous uniform F(X < 3) would be the same as F(X <= 3), yes?

The keyword threw me as I was doing the problem and there isn't any background information other than what I posted.


Original post by Putch1
Im confused :/ generally within 1 hour means including 1 hour?


I'm really not sure.

Logically thinking I assumed it wasn't including 1 hour but I may be wrong.
Original post by JJMills
If it said continuous uniform F(X < 3) would be the same as F(X <= 3), yes?


Yes.

What about F(X) = x, 0 <= x < 24 ?

If this is meant to be the cumulative distribution, then it should have a max value of 1, not 23.

I have interpreted this as a discrete distribution, but is it?
Reply 8
Original post by JJMills
If it said continuous uniform F(X < 3) would be the same as F(X <= 3), yes?

The keyword threw me as I was doing the problem and there isn't any background information other than what I posted.




I'm really not sure.

Logically thinking I assumed it wasn't including 1 hour but I may be wrong.


I'm thinking that you can either take it as P(x<=1) or P(x<1) because it is a continuous distribution, since P(x=1) = 0
So both probabilities would be correct. I remember my teacher telling me this.
Reply 9
Original post by ghostwalker
Yes.

What about F(X) = x, 0 <= x < 24 ?

If this is meant to be the cumulative distribution, then it should have a max value of 1, not 23.

I have interpreted this as a discrete distribution, but is it?


The question is made up and I obviously didn't put much attention into it.

I think I understand it now, thanks for your help though. :smile:

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