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# Statistical Symbols

## Statistical Symbols Here are given below statistics symbol’s, with names meanings-

<td”>variancevariance of population values

 Symbol Symbol Name Meaning ∑ summation summation – sum of all values in range of series ∑∑ double summation double summation μ population mean mean of population values E(X) expectation value expected value of random variable X E(X | Y) conditional expectation expected value of random variable X given Y var(X) variance variance of random variable X σ2 s 2 sample variance population samples variance estimator s sample standard deviation population samples standard deviation estimator std(X) standard deviation standard deviation of random variable X σX standard deviation standard deviation value of random variable X Mo mode value that occurs most frequently in population MR mid-range MR = (xmax + xmin) / 2 Md sample median half the population is below this value Q1 lower / first quartile 25% of population are below this value Q2 median / second quartile 50% of population are below this value = median of samples Q3 upper / third quartile 75% of population are below this value _ X sample mean average / arithmetic mean zx standard score X ~ distribution of X distribution of random variable X N(μ,σ2) normal distribution gaussian distribution gamma(c, λ) gamma distribution exp(λ) exponential distribution U(a,b) uniform distribution equal probability in range a,b Poisson(λ) Poisson distribution