# normalVar: Compute variance of truncated normal In selection: Correcting Biased Estimates Under Selection

## Description

Given a particular cutoff (`x`), what is the variance of the new truncated normal?

## Usage

 `1` ```normalVar(cutoff, truncMean = NULL, mean = 0, sd = 1) ```

## Arguments

 `cutoff` The cutoff value for the truncated normal `truncMean` The mean of the truncated normal. If left NULL, it will be estimated. `mean` The mean of the non-truncated distribution (defaults to zero) `sd` The sd of the non-truncated distribution (defaults to 1)

## Details

The variance of a pdf (f(x)) is computed by integrating the function x^2*f(x) from -Inf to Inf. To compute a truncated normal, the function remains the same, but the limits change (from -Inf to `cutoff`).

## Value

the variance of the tuncated normal distribution

Dustin Fife

## Examples

 ```1 2 3 4 5``` ```### compute variance of a distribution cutoff at zero normalVar(1) ### compare to simulated data x = rnorm(10000000, 0, 1) var(x[x>1]) ```

selection documentation built on May 30, 2017, 5:27 a.m.