# Statistical basic concepts

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Discrete Data A set of data is said to be discrete if the values / observations belonging to it are distinct and separate, i.e. they can be counted (1,2,3,....). Examples might include the number of kittens in a litter; the number of patients in a doctors surgery; the number of flaws in one metre of cloth; gender (male, female); blood group (O, A, B, AB).

## Central Limit Theorem

In probability theory , the normal (or Gaussian ) distribution is a continuous probability distribution , defined by the formula The parameter μ in this formula is the mean or expectation of the distribution (and also its median and mode ). The parameter σ is its standard deviation ; its variance is therefore σ 2 . A random variable with a Gaussian distribution is said to be normally distributed and is called a normal deviate . If μ = 0 and σ = 1 , the distribution is called the standard normal distribution or the unit normal distribution , and a random variable with that distribution is a standard normal deviate .