When do you know when to use t-distribution opposed to the z-distribution?

Answer 1

z- statistics is applied under two conditions:

1. when the population standard deviation is known.

2. when the sample size is large.

In the absence of the parameter sigma when we use its estimate s, the distribution of z remains no longer normal but changes to t distribution.

this modification depends on the degrees of freedom available for the estimation of sigma or standard deviation.

hope this will help u....

mona upreti..

:)

Answer 2

You use the t-distribution as opposed to the z-distribution when:

(1) you are testing a hypothesis about the population mean and the standard deviation is unknown (estimated from the sample).

(2) You are constructing a confidence interval for the population mean when the population standard deviation is unknown (estimated from the sample).