Why are random variables needed?

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Discussion Overview

The discussion revolves around the role and necessity of random variables (RVs) and probability mass functions (PMFs) in probability theory and statistics. Participants explore the mapping of experimental outcomes to real numbers and probabilities, questioning the efficiency and implications of these mappings.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that a random variable maps an experimental outcome to a real number, while a PMF provides the probability of that number occurring.
  • There is a question about why it is necessary to use a random variable to map outcomes to real numbers before mapping those numbers to probabilities, suggesting a potential simplification.
  • One participant suggests that using random variables allows for a fixed probability distribution, which can be more convenient than redefining the distribution for each random variable.
  • Another participant notes that random variables help maintain the independence of the probability density function (pdf) from individual experiments.
  • It is mentioned that in statistics, sampling distributions, such as the sample mean and variance, are examples of random variables that can provide insights based on the original distribution.

Areas of Agreement / Disagreement

Participants express some agreement on the utility of random variables in maintaining independence from experimental outcomes, but the discussion includes questions and uncertainties about the necessity of the mapping process itself. No consensus is reached regarding the optimal approach to mapping outcomes to probabilities.

Contextual Notes

Participants do not fully resolve the implications of using random variables versus directly mapping outcomes to probabilities, leaving open questions about the efficiency and necessity of the established methods.

dionysian
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please corret me if i am incorrect in my understanding of a RV,PMF or anything else but as i understand it a random variable simply maps a expirmental outcome to a real number. And a probability mass function simply gives the probability that a number will occur.

Now my question is this: why can't we simply map a expiremental outcome to a probability rather than use a random variable to map from the sample space a to a real number then the map a real number to a probability via the PMF?
 
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dionysian said:
please corret me if i am incorrect in my understanding of a RV,PMF or anything else but as i understand it a random variable simply maps a expirmental outcome to a real number. And a probability mass function simply gives the probability that a number will occur.

Now my question is this: why can't we simply map a expiremental outcome to a probability rather than use a random variable to map from the sample space a to a real number then the map a real number to a probability via the PMF?

a random variable is a function of the experimental outcomes. It is convenient not to redefine your probability distribution in terms of every random variable but to keep a fixed probability distribution and then look at the statistics of different random variables.
 
Ahh this is what i suspected... So its fair to say that the RV helps keeps the pdf independent of each expirment
 
dionysian said:
Ahh this is what i suspected... So its fair to say that the RV helps keeps the pdf independent of each expirment

yes.

Typically in statistics you look at sampling distributions. The sample mean and variance are example of random variables on the sampling distribution. If one knows something about the original distribution - say that is is normally distributed - then you know something about the distribution of the mean and the variance.
 

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