When do we use t test?when nominal data is givenWhen n is greater than or equal to 30When ordinal data is givenWhen n < 30

We use a t-test in statistics to compare the means of two groups and determine if there is a significant difference between them. This test is used when the sample size (n) is less than 30 and when the data is interval or ratio level (continuous).

So, among the options you provided, we use a t-test when n < 30.

We do not use a t-test for nominal or ordinal data because these types of data do not provide information about differences in means. Nominal data is categorical and does not have a numerical value or order, while ordinal data has a clear order but the differences between the values are not consistent.

Also, when n is greater than or equal to 30, we usually use a z-test instead of a t-test. This is because as the sample size increases, the t-distribution approaches the standard normal distribution (z-distribution), and the z-test is more appropriate for larger sample sizes.