# z.test

0th

Percentile

##### Z test for known population standard deviation

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

Keywords
htest
##### Usage
z.test(x, mu = 0, stdev, alternative = c("two.sided", "less", "greater"), sd = stdev, conf.level = 0.95, ...)
##### Arguments
x
Vector of data values.
mu
Hypothesized mean of the population.
stdev
Known standard deviation of the population.
alternative
Direction of the alternative hypothesis.
sd
Alternative to stdev
conf.level
Confidence level for the interval computation.
...
##### 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 since 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.

t.test, print.htest
x <- rnorm(25, 100, 5)
z.test(x, 99, 5)