Binomial Distribution

An experiment is modeled on the binomial distribution if:

1. In each trial of the experiment there are only two possible outcomes: the event A (success) and its opposite suceso contrario.

2.The probability of event A is a constant that does not vary from one test to another. It is denoted by p.

3.The probability of suceso contrario is 1 − p.

4.The outcome obtained in each trial is independent of the previous outcomes.

Random Binomial Variable

The binomial variable is a discreet random variable that can only take the values 0, 1, 2, 3, 4, ..., n assuming that n trials have been conducted.


k = 6, when flipping a coin 10 times and 6 heads are obtained.

Binomial Distribution

The binomial distribution is usually expressed by B(n, p).

Binomial Distribution Formula

n is the number of trials

k is the number of successes.

p is the probability of success.

The binomial coefficient Binomial Coefficient


The latest novel by an author has been very successful to the point that 80% of avid readers have already read it.

1. What is the probability that within a group of four avid readers, exactly two of them have already read the novel?

n = 4

p = 0.8

1 − p = 0.2

B(4, 0.8)

Binomial Distribution Solution

2.What about a maximum of two people?

Binomial Distribution Operations

Binomial Distribution Solution

Expected Value

Expected Value Formula


Variance Formula

Standard Deviation

Standard Deviation Formula


The probability of a defective item produced by a factory is 0.02. If a shipment of 10,000 items are sent to a store, determine the expected number of defective items, the variance and standard deviation for the shipment.

Expected Value Exercise

Variance Exercise

Standard Deviation Exercise