Bestea produces a 473-milliliter (ml) bottle of sweetened green iced tea. There is some variation from bottle to bottle because the filling machinery is not perfectly precise. Data on past production shows that the distribution of the contents is close to Normal, with standard deviation s = 2.1 ml. To assess the state of the bottling process, 50 bottles were randomly selected from the streaming high volume production line. The sample mean content is found to be 474.2 ml. Is this value convincing evidence that the mean fill of all bottles produced by the current process differs from the desired level of 473 ml.?
The hypotheses: H0: m = 473 and HA: m ≠ 473. The estimate is the sample mean.
Calculate the value of the test statistic z. Enter your answer to 2 decimal places of accuracy.