airline companies are interested in the consistency of the number of babies on each flight so that they have adequate safety equipment. they are also interested in the variation in the number of babies. suppose that an airline executive believes the average number of babies on flights is six with a variance of nine at most. the airline conducts a survey. the results of the 18 flights surveyed give a sample average of 6.4 with a sample standard deviation of 3.9. to test the null hypothesis against the alternative hypothesis one relies on the chi-squared test. what is the test statistic?