* *Quantitative/numerical variable is also called as '''covariate''' when it is an explanatory (independent) variable
* *Categorical/nominal variable is also called as '''factor''' when it is an explanatory (independent) variable
==Ratio, Rate, Proportion==
==Probability, Likelihood==
===Probability===
Given a dataset of a sample <math>X = ( x_1,\ x_2,\ x_3,\ \cdots )</math> derived from a population, the sample mean <math>\bar{X}</math> and the sample standard deviation <math>s</math> can be calculated.
Chance that a value in <math>X</math> is in a range of certain values like <math-->x_i > n</math> can also be calculated from the dataset. This chance is <math>probability</math>.:<math>probability = P(x_i>n|\bar{X},s)</math>For example, if a dice was rolled 600 times and numbers of 1 to 6 appeared 100 times for each, the mean is 3.5 and the standard deviation is 1.71. ''see'' [[Data distribution#Probability that a value is 1 in that sample is, :<math>probability = P(x_i=1Likelihood|3.5'Probability,1.71) = 100/600 = 1/6 </math>===Likelihood===' in 'Data distribution']]