D’Alessandro et al. (A3) wished to know if preexisting airway hyperresponsivenes
ID: 3337435 • Letter: D
Question
D’Alessandro et al. (A3) wished to know if preexisting airway hyperresponsiveness (HR) predisposes subjects to a more severe outcome following exposure to chlorine. Subjects were healthy volunteers between the ages of 18 and 50 years who were classified as with and without HR. The following are the FEV1 and specific airway resistance (Sraw) measurements taken on the subjects before and after exposure to appropriately diluted chlorine gas:
(a) Perform a statistical analysis of the data (including hypothesis testing and confidence interval
construction) that you think would yield useful information for the researchers.
(b) State all assumptions that are necessary to validate your analysis.
(c) Find p values for all computed test statistics.
(d) Describe the population(s) about which you think inferences based on your analysis would be
applicable.
Hyperreactive Subjects Normal Subjects Pre-Exposure Pt Exposure Pre-Exposure Subject FEV Subject FEV Post-Exposure Sraw Sraw FEV Sraw Subjeot Sraw FEV I 3.0 4.1 3.4 3.3 3.3 5.80 9.56 7.84 6.41 9.12 1.8 3.7 3.0 3.0 3.0 21.4 1 12.5 2 14.3 3 3.9 3.6 3.6 5.1 5.52 6.43 5.67 3.77 5.53 3.7 3.3 3.5 4.9 8.70 6.94 10.00 4.54 .37 3 17.1 5 A3. ALEssANDRA D'ALESSANDRO,WARE KUSHNER, HoFERWONG, HoMER A. BouSHEY, and PAUL D. BLANC, "Exaggerated Responses to Chlorine Inhalation Among Persons with Nonspecific Airway Hyperreactivity," Chest, 109 (1996), 331-337.Explanation / Answer
a. Poolted t test variance test for comparing the means of the two independent populations, 1. Hyperreactive population, and 2. Normal population with the sample hyperreactive and normal subjects of size 5 numbers each. First the mean value of the two independent samples under the pre and post exposure measurements under FEV1 compared. Refer sheet : Pooled t FEV1 in this workbook. Test statistics t= -2.0283. The p-value of 0.0771 is greater than the alpha value of 0.05 , so we do not have sufficient evidence to support the claim, that the sample variances of the the hyperreactive and the normal subjects in the Pre exposure FEV1 condition is equal.
But the post exposure data analysis shows that the sample means are not same, with the p-value of 0.044 which is less than alpha value, we have sufficient evidence to prove that they are different. That means that under the post exposure, FEV1 data for hyperreactive subjects are different compared to the normal subjects.
Further to this, Pooled t test results for the hyper reactive and normal subjects for their level of specific resistance to airway is not the same. There are different for pre and post exposure.
Upper tail test with the paired t test statistics, it is evident that we do not have sufficient to accept the claim that the hyperreactive subjects are not more susceptive post exposure in sraw data. The outcome of the HR subjects is more compared to the pre exposure data.
b) Assumptions are the sample data taken from two independent population viz, hyperreactive and normal subject. Sample data are simple random independent samples that are normally distributed. The mean is zero and the standard deviation of the population parameter is 1.
c) Inference of the more severe outcome in the post exposure condition is applicable to both the normal as well as hyperreactive population. But the hyper reactive population is affected more than the normal subjects.
Excel Sheet is uploaded: https://drive.google.com/open?id=0B80BcTXHVvxvNUF5RDlMZk1qb2c
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