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Continuous probability distributions describe random variables through probability density functions (PDFs), denoted as f(x). Unlike discrete variables, the probability of any specific value in continuous variables is zero. This guide explains the computation of probabilities, expected values, and variances for various distributions, including uniform, normal, and exponential distributions. Additionally, it discusses relationships between these distributions, such as normal vs. standard normal and Poisson vs. exponential distributions, providing a comprehensive overview for statistical analysis.
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Probability density function • With continuous ransom variables, the counterpart of the probability function is the probability density function, denoted by f(x) <Note> How to compute Pr(a≤x≤b)? <Note>The probability of any particular value of the continuous random variable is zero.
Continuous probability distribution • For a continuous random variable x: • The probability distribution is defined by a probability density function, denoted by f(x) • The expected value of a continuous random variable is a measure of the central location for the random variable. • The variance is used to summarize the variability in the values of a random variable.
Uniform probability distribution • Uniform probability density function: • Expected value for uniform probability distribution: • Variance for uniform probability distribution: f (x) = 1/(b – a) for a<x<b = 0 elsewhere E(x) = (a + b)/2 Var(x) = (b - a)2/12
Normal probability distribution • Normal probability density function: • Expected value for normal probability distribution: • Variance for normal probability distribution:
Standard normal probability distribution • Standard normal probability density function: • Expected value for standard normal probability distribution: 0 • Variance for standard normal probability distribution: 1
Exponential probability distribution • Exponential probability density function: • Expected value for exponential probability distribution: • Variance for exponential probability distribution:
Other distributions • Chi-square distribution • t distribution • F distribution • others
Relationships between distributions • Normal distribution vs. Standard normal distribution • Normal distribution vs. Binomial distribution • Poisson distribution vs. Exponential distribution