Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I wanted to clearly understand these notations on probability.

  1. Oct 29, 2012 #1
    Hi all,
    I would like to make things clear about the notations used in probability. what does X and x in pdf
    f[itex]_{X}[/itex](x) means.

    -Devanand T
     
  2. jcsd
  3. Oct 29, 2012 #2
    Well, it means whatever the person who wrote it decides that it means. I would guess that fX() is a random function, and x is some sort of value. Like fX(x) could be equal to x + X.
     
  4. Oct 29, 2012 #3

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    The uppercase X designates the random variable. The lowercase x designates some particular value of the random variable.
     
  5. Oct 29, 2012 #4

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    No, it doesn't mean "whatever the person who wrote it decides that it means", and it's best not to guess when you don't know the answer. Suppose you're reading up on chemistry and you come across H2O. This doesn't mean whatever the author intended. It has a very specific meaning. It's water. Similarly, the nomenclature [itex]f_X(x)[/itex] is widely used to mean the probability density function or probability mass function for some random variable [itex]X[/itex]. That nomenclature is standard, just as is H2O.
     
  6. Oct 29, 2012 #5
    Thank you sir for the reply.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: I wanted to clearly understand these notations on probability.
  1. Probability notation (Replies: 3)

Loading...