Twenty-two young asthmatic volunteers were studied to assess the short-term effects of sulfur dioxide (SO₂) exposure under various conditions. The baseline data were recorded regarding bronchial reactivity to SO₂ stratified by lung function (as defined by forced expiratory volume / forced vital capacity [FEV1/FVC]) at screening.

Lung-function group
Group one FEV/FVC 74%	Group two FEV/FVC 75-84%	Group three FEV/FVC 85%
20.8	7.5	9.2
4.1	7.5	2.0
30.0	11.9	2.5
24.7	4.5	6.1
13.8	3.1	7.5
	8.0
	4.7
	28.1
	10.3
	10.0
	5.1
	2.2

1) Identify the dependent variable and the independent or explanatory variable(s) in this study. Also, state the Null and Alternative hypotheses.

2) If this null hypothesis is true, then we would expect to see that the average variation between the means (i.e., the "model mean square" in SAS) is equal to the average variation within each group (i.e., the "error mean square" in SAS). We compare the two mean squares as an F ratio, dividing the model mean square by the error mean square.

Locate the two mean squares on the SAS output table and calculate the F ratio. Show your work.

3) Report the test statistic and P-value from the SAS output. Based on that information, what conclusion can you make about the Omnibus (or Overall) Null hypothesis(i.e. Reject or Fail to Reject the Null)?

4) Based on the information from the Student-Newman-Keuls post hoc test, what groups (GRP) are significantly different from each other and what groups are not? [Be sure your answer is thorough ... there's a lot of groups to consider!]

5) Interpret these findings (3-4 sentences max). Your answer should (1) restate the findings, (2) note the generalizability of these results, and (3) state what these findings mean from clinical perspective.