# interval_estimate2: Two sided interval estimation of 'mu1-mu2' of two normal... In OneTwoSamples: Deal with One and Two (Normal) Samples

 interval_estimate2 R Documentation

## Two sided interval estimation of `mu1-mu2` of two normal samples

### Description

Compute the two sided interval estimation of `mu1-mu2` of two normal samples when the population variances are known, unknown equal, or unknown unequal.

### Usage

``````interval_estimate2(x, y, sigma = c(-1, -1), var.equal = FALSE, alpha = 0.05)
``````

### Arguments

 `x` A numeric vector. `y` A numeric vector. `sigma` A numeric vector of length 2, which contains the standard deviations of two populations. When the standard deviations are known, input it, then the function computes the interval endpoints using normal population; when the standard deviations are unknown, ignore it, now we need to consider whether the two populations have equal variances. See `var.equal` below. `var.equal` A logical variable indicating whether to treat the two variances as being equal. If `TRUE` then the pooled variance is used to estimate the variance otherwise the Welch (or Satterthwaite) approximation to the degrees of freedom is used. `alpha` The significance level, a real number in [0, 1]. Default to 0.05. 1-alpha is the degree of confidence.

### Value

A data.frame with variables:

 `mean ` The difference of sample means xb-yb. `df ` The degree of freedom. `a ` The confidence lower limit. `b ` The confidence upper limit.

### Author(s)

Ying-Ying Zhang (Robert) robertzhangyying@qq.com

### References

Zhang, Y. Y., Wei, Y. (2013), One and two samples using only an R funtion, \Sexpr[results=rd]{tools:::Rd_expr_doi("10.2991/asshm-13.2013.29")}.

### Examples

``````x=rnorm(10, mean = 1, sd = 0.2); x
y=rnorm(20, mean = 2, sd = 0.3); y

interval_estimate2(x, y, sigma = c(0.2, 0.3))
interval_estimate2(x, y, var.equal = TRUE)
interval_estimate2(x, y)
``````

OneTwoSamples documentation built on March 31, 2023, 11:49 p.m.