In probability theory the binomial distribution is the discrete probability distribution that gives only two possible results in an experiment, either Success or Failure . For example, if we toss a coin, there could be only two possible outcomes: heads or tails, and if any test is taken, then there could be only two results: pass or fail. This distribution is also called a binomial probability distribution. There are two parameters n and p used here in a binomial distribution. The variable ‘n’ states the number of times the experiment runs and the variable ‘p’ tells the probability of any one outcome ..
Suppose you are tossing a coin 3 times We can easily find the probability for getting 2 heads i.e 3/8. and the sample space will be 8 i.e 2 3. If we want to toss a coin ten times then the sample space will be 1024 i.e 2 10 So in that case we use Binomial distribution. A single success/failure test is also called a Bernoulli trial or Bernoulli experiment, and a series of outcomes is called a Bernoulli process .
EXAMPLES Taking a survey of positive and negative reviews from the public for any specific product or place. By using the YES/ NO survey, we can check whether the number of persons views the particular channel. To find the number of male and female employees in an organisation .
The binomial distribution formula is for any random variable X, given by ;
n = the number of experiments x = 0, 1, 2, 3, 4, … p = Probability of Success in a single experiment q = Probability of Failure in a single experiment = 1 – p The binomial distribution formula can also be written in the form of n-Bernoulli trials, where n C x = n!/x!(n-x)!.
FOR BINOMIAL DISTRIBUTION Mean , μ = np Variance, σ 2 = npq Standard Deviation σ= √( npq ) Where p is the probability of success q is the probability of failure, where q = 1-p
Properties of Binomial Distribution The properties of the binomial distribution are: There are two possible outcomes: true or false, success or failure, yes or no. There is ‘n’ number of independent trials or a fixed number of n times repeated trials. The probability of success or failure remains the same for each trial. Only the number of success is calculated out of n independent trials. Every trial is an independent trial, which means the outcome of one trial does not affect the outcome of another trial.
Q1.If a coin is tossed 5 times, find the probability of: (a) Exactly 2 heads (b) At least 4 heads.