Probability of Observing a Rare Event

Description

This program calculates probabilities for observing an event at least once, given the true probability inputs. Creates a table that can display multiple probabilities.

Input Items

• True Event Probabilities: A comma- or space-separated list of probabilities.
• Sample Size: Enter n, the planned sample size.

Output Items

• A table of probabilities.

Statistical Code

The program is written in R.

View Code

function(event_rates, sample_size)
{
    event_probabilities = data.frame(n = numeric(),
                                     rate = numeric(),
                                     probability = character())
    for (event_rate in unique(event_rates)) {
        event_probability = paste0(round((1 - ((1 - event_rate)^sample_size)) * 100, 1), "%")
        event_probabilities = rbind(event_probabilities,
                                    data.frame(n = sample_size,
                                               rate = event_rate,
                                               probability = event_probability))
    }

    result = list(event_probabilities = event_probabilities)
    return(jsonlite::toJSON(result, pretty = TRUE))
}