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Binomial distributions have two choices – usually “success” or “failure” in an experiment. This binomial distribution calculator can help you solve bimomic problems using no tables or long equations. You will need to know a couple of key items to connect to the calculator and then you will be set!

Probability(P) – percentage or decimal

Number of tests (n)

Successes (X) – ratings are acceptable, e.g. an X from 0 to 4 successes

For the first box (p), insert the probability of success in a test as a decimal place. This may be given to you as a percentage (i.e. 80% of respondents…), or it may be given to you as a word problem that you have to convert to a decimal (i.e. a multiple choice test with four answers would have a probability of 0.25 of a correct answer each time you guessed).

In the second box, enter the number of tests (n).

The next two boxes, X1 and X2, enable you to enter a range, i.e. from 0 to 4 you would enter 0 in box X1 and 4 in box X2. If instead of an interval, you want an exact number, enter the number twice at a time in each box (i.e. for “exactly 9” you will enter 9 in both X1 and X2).

The way mortal humans do it

Whether you are like most people, trying to use a formula over and over again to get the answers you want doesn’t sound like fun!

The majority of people use a binomial distribution table to look for the answer, like the one on this site. The problem with most tables, including the one here, is that it doesn’t cover all the possible values of p, or n. So if you have p = .64 and n = 256, then you probably won’t be able to just look for it in a table.


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