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Statistics · Statistical distributions

Chapter 1 · 3

The idea

The binomial distribution as a model

When the count of "successes" in a fixed number of repeated trials follows a binomial distribution X ~ B(n, p): the four conditions (a fixed number of trials, two outcomes per trial, a constant probability of success, and independent trials), how to identify n and p from a context, how to state a condition for a binomial model, and when the binomial is NOT appropriate.

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Statistics · Statistical distributions

The binomial distribution as a model

When the count of "successes" in a fixed number of repeated trials follows a binomial distribution X ~ B(n, p): the four conditions (a fixed number of trials, two outcomes per trial, a constant probability of success, and independent trials), how to identify n and p from a context, how to state a condition for a binomial model, and when the binomial is NOT appropriate.

Why it works

Counting successes in repeated trials

Many situations are the same experiment repeated over and over, where each repeat either "succeeds" or "fails". If you count the number of successes, that count often follows a binomial distribution, written

X∼B(n,p),X \sim B(n, p),

where nn is the number of trials and pp is the probability of success on each trial. (So in B(15,0.48)B(15, 0.48), there are n=15n = 15 trials each with success probability p=0.48p = 0.48.)

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