Project #45119 - Stats Problem

2.  A study published in the American Journal of Public Health examined the accuracy of weight loss information found through web searches (Modave et al., Analysis of the Accuracy of Weigh Loss Information Search Engine Results on the Internet, AJPH Oct. 2014).  The ‘subjects’ for these analyses were web sites, and each web site was graded on the accuracy of its weight loss information.  Accuracy scores could range from 0 to 28, with higher values indicating better accuracy.  Web sites were also categorized by type of site, and we are interested in whether the accuracy of weight loss information differs by type of site.  Below is a summary of weight loss accuracy scores for medical/university/government, blog, and commercial sites:

 

 

Type of Web Site

 

Med/Uni/Gov

Blog

Commercial

N

Mean

Std Dev

14

10.67

3.17

7

10.81

2.35

21

5.92

3.42

 

2A.  Does the accuracy of weight loss information differ between medical/university/government sites and commercial web sites?  Test through an appropriate procedure.  Report the statistical procedure used, value of the test statistic, degrees of freedom, and two-tailed p-value, and give a summary statement of your results.

 

 

2B.  (No calculations needed)  To compare the accuracy of weight loss information presented in blogs vs. medical/university/government sites, an investigator calculated the difference in mean accuracy scores for these types of sites (10.81 – 10.67 = 0.14) and the 95% CI for this difference (-2.70 , 2.98).   What can you conclude about the significance of the difference in accuracy between these two types of sites, based on this confidence interval?  Explain.


 

3.  A study published in the American Journal of Public Health examined compared smoking behavior among adults with and without mobility impairments (Borrelli et al., Cigarette Smoking among Adults with Mobility Impairment: A US Population-Based Survey, Oct. 2014).  The following summaries are based on this article, although sample sizes have been changed (the article was based on a survey of 32,000 adults) and the analyses simplified a bit.

 

The following gives the number and percent of current smokers, for those with and without mobility impairments, for respondents between the ages of 21 and 44:

 

Mobility

Impairment

No Mobility

Impairment

Total n

n smoking

Percent smoking

150

58

38.7

 

2000

430

21.5

 

3A.  Give the 95% confidence interval for the percent of young adults (ages 21 to 44) without mobility impairment who smoke, and give an interpretation of this confidence interval. 

 

 

 

3B.  Are young adults with mobility impairment more likely to smoke than young adults without mobility impairment?  Test through an appropriate statistical procedure, reporting the procedure used, the value of the test statistic, degrees of freedom, two-tailed p-value, and give a summary of your conclusion.

 

Chi square=23.534; d.f.=1; p-value=1.23E-6; Reject the null: those with mobility impairment are significantly more likely to smoke than those without mobility impairment.

 

3C.  (No calculations necessary)  For older adults (ages 65+), 8.2% of those with mobility impairment smoked, compared to 7.6% of those without mobility impairment.  The p-value comparing these two percentages was p=0.603.  Are older adults with mobility impairment more likely to smoke than older adults without mobility impairment?  Explain.

 

 

 

Subject Mathematics
Due By (Pacific Time) 10/27/2014 09:40 am
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