Dice-like probability calculator
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Dice-like probability calculator
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Uses the binomial distribution function
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BINOMDIST(num_successes, num_trials, prob_success, cumulative)
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that calculates (independent; see below)
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the number of successes, num_successes
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in a number of rolls, num_trials
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when there is a known probability of success in each roll, prob_success
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with an option to count any outcome with num_successes or fewer, cumulative
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Intuitive input (entered)
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Number of sides on dice6
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Total number of dice rolls (or dice in one roll)7
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Number of matches sought2or fewer
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Enter 0, -1, or 1 for "exactly", "or fewer" or "or more"
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Formula input (calculated)
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intercept0
Since the binomial distribution formula can only tell us "or fewer", if we want to know "or more", we have to calculate "or fewer" for failures (1 - successes). So we set this to 1 for "or more" calculations.
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slope1
Since the binomial distribution formula can only tell us "or fewer", if we want to know "or more", we have to calculate "or fewer" for failures (1 - successes). So we set this to -1 for "or more" calculations.
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num_successes2
We use the intercept and slope to convert our intuitive request into an "or fewer" request. If we are asking for "or more", this is really the maximum number of failures we will allow.
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num_trials7
This is the number of rolls. No conversion.
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prob_success0.1666666667
We use the intercept and slope to convert the number of sides on the dice into a probability of success. Ideally just 1/sides. But if we are asking for "or more", this is really the probability of not rolling a match.
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cumulativeTRUE
Unless we are asking for the probability of exactly a number of successes, we use TRUE here for the spreadsheet formula so it will give us its "or fewer" result.
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Result
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Probability90.422%
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