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Peak expiratory flow (PEF) is a measure of a patient's ability to expel air from the lungs. Patients with asthma or other respiratory conditions often have restricted PEF. The mean PEF for children free of asthma is 306. An investigator wants to test whether children with chronic bronchitis have restricted PEF. A sample of 40 children with chronic bronchitis is studied and their mean PEF is 279 with a standard deviation of 71. Is there statistical evidence of a lower mean PEF in children with chronic bronchitis? Run the appropriate test at α=0.05.
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Consider again the study in Problem 1, a different investigator conducts a second study to investigate whether there is a difference in mean PEF in children with chronic bronchitis as compared to those without. Data on PEF are collected and summarized below. Based on the data, is there statistical evidence of a lower mean PEF in children with chronic bronchitis as compared to those without? Run the appropriate test at α =0.05.
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Group
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Number of Children
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Mean PEF
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Std Dev PEF
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Chronic Bronchitis
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25
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281
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68
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No Chronic Bronchitis
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25
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319
|
74
|
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A clinical trial is run to assess the effects of different forms of regular exercise on HDL levels in persons between the ages of 18 and 29. Participants in the study are randomly assigned to one of three exercise groups - Weight training, Aerobic exercise or Stretching/Yoga - and instructed to follow the program for 8 weeks. Their HDL levels are measured after 8 weeks and are summarized below.
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Exercise Group
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N
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Mean
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Std Dev
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Weight Training
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20
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49.7
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10.2
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Aerobic Exercise
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20
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43.1
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11.1
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Stretching/Yoga
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20
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57.0
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12.5
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Is there a significant difference in mean HDL levels among the exercise groups? Run the test at a
5% level of significance. HINT: SSerror = 7286.5.