Assignment:
Calculating Degrees of Freedom How is the number of degrees of freedom for shown below and 10 affected if Formula 9-1 is used instead of selecting the smaller of n1 - 1and n2- 1? If Formula 9-1 is used for the number of degrees of freedom instead of the smaller of n1 - 1and n2- 1 ,how are the hypothesis test and the confidence interval affected? In what sense is "d = smaller of n1 - 1and n2- 1" a more conservative estimate of the number of degrees of freedom than the estimate obtained with Formula 9-1?
Assume that the two samples are independent simple random samples selected from normally distributed populations. Do not assume that the population standard deviations are equal, unless your instructor stipulates otherwise.
Exercise
Hypothesis Test of Effectiveness of Humidity in Treating Croup In a randomized controlled trial conducted with children suffering from viral croup, 46 children were treated with low humidity while 46 other children were treated with high humidity. Researchers used the Westley Croup Score to assess the results after one hour. The low humidity group had a mean score of 0.98 with a standard deviation of 1.22 while the high humidity group had a mean score of 1.09 with a standard deviation of 1.11 (based on data from "Controlled Delivery of High vs Low Humidity vs Mist Therapy for Croup Emergency Departments," by Scolnik, et al., Journal of the American Medical Association, Vol. 295, No. 11). Use a 0.05 significance level to test the claim that the two groups are from populations with the same mean. What does the result suggest about the common treatment of humidity?
Exercise
Confidence Interval for Effectiveness of Humidity in Treating Croup Refer to the sample data given shown below and construct a 95% confidence interval estimate of the difference between the mean Westley Croup Score of children treated with low humidity and the mean score of children treated with high humidity. What does the confidence interval suggest about humidity as a treatment for croup?