The test statistic table shows the results of the one-sample t test.

- The t column displays the observed t statistic for each sample, calculated as the ratio of the mean difference divided by the standard error of the sample mean.

- The df column displays degrees of freedom. In this case, this equals the number of cases in each group minus 1.

- The column labeled Sig. (2-tailed) displays a probability from the t distribution with 15 degrees of freedom. The value listed is the probability of obtaining an absolute value greater than or equal to the observed t statistic, if the difference between the sample mean and the test value is purely random.

- The Mean Difference is obtained by subtracting the test value (322 in this example) from each sample mean.

- The 90% Confidence Interval of the Difference provides an estimate of the boundaries between which the true mean difference lies in 90% of all possible random samples of 16 disc brakes produced by this machine.

Since their confidence intervals lie entirely above 0.0, you can safely say that machines 2, 5 and 7 are producing discs that are significantly wider than 322mm on the average. Similarly, because its confidence interval lies entirely below 0.0, machine 4 is producing discs that are not wide enough.