Which symbol is used to represent a variate?

In statistics, a variate refers to a random variable or a measurable quantity that can take on different values. The common notation for representing variates typically involves capital letters, particularly 'X', which is widely recognized as a standard symbol for a random variable.

In statistical modeling, 'X' often represents independent variables or predictors in regression analysis. This notation is crucial because it allows analysts to consistently denote varying quantities across different statistical contexts. Choosing 'X' specifically aligns with conventions in probability and statistics, which makes it the correct answer among the listed options.

The other symbols mentioned do not conventionally represent variates. For instance, 'y' is frequently used for dependent variables in regression, 'b' can symbolize coefficients in the context of regression equations, and 'n' usually denotes sample size or the number of observations. Thus, 'X' is the most appropriate and universally accepted symbol for denoting a variate.