▪The value of T is zero if there is no difference in the data.

▪The simplest use of the one-sample T-test is when testing whether the mean of a variable already coded in columns of the data is zero.

▪There might be occasions when you want to use a one-sample T-test on values that are not the same as those in the data.

▪To test whether a mean can be different from a non-zero value, subtract that value from each data value. In other words, to test whether the mean number of visits to a supermarket is equal to 2, you actually test whether the mean of (number of visits to supermarket – 2) is equal to 0.

▪To make a paired test between two data values, test whether the difference between them is zero.