1

Suppose we toss a coin which is not fair. and the probability of success is 0.7. Is that enough to decide on the shape of it beta distribution ? what would be its shape then ?

As far as I know, it's the probability of success that we map in the X-axis. so, it should be between 0 and 1. But in some articles and books I've found, x axis has some values beyond that. I'm confused.

pls help

Kots
  • 486
  • 1
  • 5
  • 21
Prasadika
  • 897
  • 2
  • 20
  • 36

2 Answers2

2

A random variable is a mapping from random outcomes of any sort into the number line. For a categorical random variable, the categorical outcomes are mapped to numeric outcomes such as 0 for failure, 1 for success. Probability distributions are then a mathematical description of the relative likelihood of a random variable's different values. They are usually expressed in terms of the set of possible outcomes along the X-axis, and either the corresponding probability or density (for discrete or continuous, respectively) along the Y-axis.

Why do you think a coin toss should have a beta distribution? The beta distribution is a continuous distribution, meaning there are an infinite number of possible outcomes it can have. Your coin toss can only have two possible outcomes, heads or tails. That's described by a classic Bernoulli random variable with p = 0.7 for "success" and, implicitly, q = 1-p = 0.3 for failure.

pjs
  • 18,696
  • 4
  • 27
  • 56
1

Regarding the

I've found, x axis has some values beyond that.

you may refer to to Beta distribution with arbitrary domain, sometimes used to model activity durations in PERT with PDF in the domain [c,c+d] (not [0,1]):
http://www.math.uah.edu/stat/special/Beta.html

Community
  • 1
  • 1
Kots
  • 486
  • 1
  • 5
  • 21