z.test {NCStats} R Documentation

## Z test for known population standard deviation

### Description

Compute the test of hypothesis and compute confidence interval on the mean of a population when the standard deviation of the population is known.

### Arguments

 `x` Vector of data values `mu` Hypothesized mean of the population `sd` Known standard deviation of the population `alternative` Direction of the alternative hypothesis `conf.level` Confidence level for the interval computation `...` Additional arguments are silently ignored

### Details

Most introductory statistical texts introduce inference by using the Z test and Z based confidence intervals based on knowing the population standard deviation. Most statistical packages do not include functions to do Z tests because the T test is usually more appropriate for real world situations. This function is meant to be used during that short period of learning when the student is learning about inference using Z procedures, but has not learned the T based procedures yet. Once the student has learned about the T distribution the `t.test` function should be used instead of this one (but the syntax is very similar, so this function should be an appropriate introductory step to learning `t.test`).

### Value

An object of class `htest` containing the results

### Note

This function should be used for learning only, real data should generally use `t.test`.

### Author(s)

This is `z.test` in TeachingDemos but imported and exported here.

`t.test`
```z.test(rnorm(25,100,5),99,5)