Variable - Random Variable

[Ranjith]

How does one can understand the difference between the "VARIBLE" and "RANDOM VARIABLE"?

[Gandalf]

That question is way too vague. You need to give more context for "variable".

Here's a simple definition of random variable I found on-line A variable whose values are random but whose statistical distribution is known.E.g. roll a fair die. The number that comes up is a random variable. You don't know, until you roll, what it will be, but you do know, before it is rolled, that the probability it is a 1 is 1/6.

[herrMrtn]

Are you sure it's worth your time to be hung up on the basic meaning of words? You've got an exam to study for (I presume, since you're posting in this subforum)!

[Ranjith]

Let T be the future lifetime of a life aged (x).

Case 1
Suppose we know the distribution(pdf or cdf) of T.

Case 2
Suppose we don't know the distribution of T. (or not suffiecient data to justify..)

Case 1, T is a random variable
Case 2, ??????

Thanks

Note: Understanding basic concepts are very important than pass the exams-to do something NEW....!

[herrMrtn]

Seriously?

Okay. Let's say there is a value in a system denoted by x; if x can take on multiple values then it is a variable. If, given all non-random inputs into the system, the value of x cannot be absolutely determined, then it is a random variable. Who says we must know the distribution in order to call it random?

My sincere advice is to not be hung up on details. You don't need to be a mechanic to drive a car; same goes for math and actuarial applications.