Z-test

A z-test is used when we wish to test the value of the mean of a population, which we know can be modelled by the normal distribution, and we know the value of the population variance.

When you formulate a test there are a number of fixed elements.

For the z-test these are:

-the  null hypothesis  μ =… and σ =… (mu and sigma)

-left side, right side or both sided

-the significance levelα (alpha)

-the size of the sample

-the average of the observations

The distribution drawn is the distribution of the mean of the sample under the null hypothesis.

The average of the sample observations is plotted with a vertical line in the diagram. By typing, or dragging the line, you can adjust the average.

There is a number of options and buttons

p-value

In the diagram, the bars corresponding to the number of successes in the sample, or more extreme numbers of successes, are colored red.

Critical region

In the diagram, the bars which correspond to the rejection of the null hypothesis test are colored red.

Normal approximation

The best-fitting normal distribution is drawn.

Formulate conclusion

With this option you obtain a detailed conclusion, the text of which can be exported as an RTF file, which almost all current text editors can read.