2024-11-17

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Probability Distributions - Continuous vs. Discrete

  • Probability distributions describe how the probabilities of different outcomes are distributed for a random variable, defining the odds of each possible value for the variable.
  • In the following slides we will explore the differences between Continuous and Discrete Probability Distributions.
  • We will also showcase some examples with plots created in R.

Discrete Probability Distributions

  • A distribution is considered discrete if the random variable can only take on a finite set of values.
  • Uses the Probability Mass Function (PMF) to determine the probabilities for each potential value.
  • Total probability cannot exceed 1, so the sum of all probabilities is equal to 1.
  • Example: Binomial Distribution.

\[ P(X = x) = \binom{n}{x}p^{x}(1-p)^{n-x} \]

Continuous Probability Distributions

  • A distribution is considered continuous if the random variable can take on any value within a provided range or interval.
  • Uses the Probability Density Function (PDF) to determine the probabilities for each potential value.
  • Total probability cannot exceed 1, so the sum of all probabilities is equal to 1.
  • Example: Normal Distribution.

\[ P(a \leq X \leq b) = \int_a^b f(x) \, dx \]

R Code for Example Binomial Distribution

binom_dist_data <- rbinom(500, size = 25, prob = 0.5) 
#generate random binom dist.

ggplot(data.frame(binom_dist_data), aes(x = binom_dist_data)) +
  geom_histogram(binwidth = 1, fill = "red", color = "black") +
  labs(
    title = "Binomial Distribution Histogram",
    x = "Number of Successes",
    y = "Frequency"
  ) +
  theme(
    plot.title = element_text(hjust = 0.5)
  )
#plot histogram with red-filled bars and black outline
#labeled both x and y axis.

Example of Binomial Distribution

  • Coin Flip Example
    • Probability of Success: 50%
    • 500 random events
    • 25 total trials

Example of Normal Distribution

  • Reaction Speed Example
    • Mean Reaction Speed: 25ms
    • Standard Deviation: 5ms
    • Participant Sample Size: 500

Younger vs. Older Reaction Speeds

  • Younger/Older Gamers with a mean of 25/35(ms) and standard deviation of 5/7(ms).