A new study suggests that women with asthma exposed to air pollution, even before conception, significantly increase their risk of delivering a premature baby. The researcher reported gestational ages for two groups of women with asthma – one group of 44 women exposed to air pollution (mean = 34 weeks with a standard deviation of 1 week) and another group of 50 women not exposed to air pollution (mean = 39 weeks with a standard deviation of 1 week). Which one of the following statements is INCORRECT? (Set alpha level at 0.05; Pooled standard deviation = 1)
a. The null hypothesis is that gestational age is not different between women with asthma who are exposed to air pollution and those who are not exposed to air pollution.
b. The ratio of variances is 1.
c. The degrees of freedom is 88.
d. The obtained test statistic is approximately -28.29.
e. The critical test statistic is 1.960.
f. The decision should be to reject the null hypothesis.