This post shows four ways to calculate the conditional probability that I have an umbrella, given that it’s raining, \(P(umbrella|raining)\). The first way uses the ratio formula, \(P(raining \land umbrella)/P(raining)\). The second uses a three-valued logical connective, the conditional event, which can be traced back to the work of Bruno de Finetti in the 1930s (see, e.g., Baratgin, 2021). The third filters the dataset to rows where it’s raining before counting the proportion of those where I had an umbrella. The fourth uses logistic regression.
Suggested citation: Fugard, A. (2024, November 2). Four ways to calculate the probability that if it rains, I have an umbrella [blog post]. https://andifugard.info/four-ways-to-calculate-the-probability-that-if-it-rains-i-have-an-umbrella/
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