1.(This begins Exercise 4 which spans questions 1 - 11)

In an August 2013 article published in American Journal of Public Health, researchers report the results of a two-site (San Francisco and NYC) randomized trial: here is a description of the trial and itsstudy sample from the article abstract:

Objectives. We evaluated the efficacy of a hepatitis care coordination intervention to improve linkage to hepatitis A virus (HAV) and hepatitis B virus (HBV) vaccination and clinical evaluation of hepatitis C virus (HCV) infection among methadone maintenance patients.

Methods. We conducted a randomized controlled trial of 489 participants from methadone maintenance treatment programs in San Francisco, California, and New York City from February 2008 through June 2011. We randomized participants to a control arm (n = 245) and an intervention arm (n = 244), which included on-site screening, motivational-enhanced education and counseling, on-site vaccination, and case management services. Of the 150 participants in the intervention group who needed the combined HAV--- HBV vaccine, 115 received the vaccine within 30 days of the vaccine being recommended. Of the 150 participants in the control group who needed the combined HAV-HBV vaccine, 18 received the vaccine within 30 days of the vaccine being recommended.

- For this study, what is the primary outcome?

a. Vaccination Status At 30 Days

b. Treatment or Control Group

2.For this study what is the primary exposure (predictor) of interest?

a. Vaccination Status At 30 Days

b. Treatment or Contol Group

3.-Estimate the risk difference (difference in proportions) of getting the vaccine within 30 day of recommendation for the intervention group compared to the control group.

a. 0.65 (65%)

b. -0.65 (-65%)

c. 6.4 (640%)

d. 0.16 (16%)

e. 24.1 (2410%)

f. 0.04 (4%)

4.- Interpret the estimate from item #3in a sentence.

a. The absolute difference in proportions (probability) of getting vaccinated within 30 days for subjects in the intervention group compared to subjects in the control group is 0.65.

b. The absolute difference in proportions (probability) of getting vaccinated within 30 days for subjects in the intervention group compared to subjects in the control group is -0.65.

c. An individual who receives the intervention has 65 times the risk (probability) of being vaccinated within 30 days compared to if this individual was in the control group.

d. An individual who receives the intervention has a 65% lower risk (probability) of being vaccinated within 30 days compared to if this individual was in the control group.

e. An individual who receives the intervention has a 65% greater odds of being vaccinated within 30 days compared to if this individual was in the control group.

f. An individual who receives the intervention has a 65% lower odds of being vaccinated within 30 days compared to if this individual was in the control group.

5.- Estimate the relative risk (risk ratio) of getting the vaccine within 30 day of recommendation for the intervention group compared to the control group

a. 0.65

b. -0.65

c. 6.4

d. 0.16

e. 24.1

f. 0.04

6.- Interpret the estimate from item #5in a sentence.

a. The absolute difference in proportions (probability) of getting vaccinated within 30 days for subjects in the intervention group compared to subjects in the control group is 0.64

b. The absolute difference in proportions (probability) of getting vaccinated within 30 days for subjects in the intervention group compared to subjects in the control group is -0.64.

c. An individual who receives the intervention has a 540% greater risk/probability (6.4 times the risk/probability) of being vaccinated within 30 days compared to if this individual was in the control group.

d. An individual who receives the intervention has a 640% lower risk/probability (- 6.4 times the risk/probability) of being vaccinated within 30 days compared to if this individual was in the control group.

e. An individual who receives the intervention has a 540 % greater odds (6.4 times the odds) of being vaccinated within 30 days compared to if this individual was in the control group.

f. An individual who receives the intervention has a 640% lower (-6.4 times the odds) odds of being vaccinated within 30 days compared to if this individual was in the control group.

7.- Estimate the relative odds (odds ratio) of getting the vaccine within 30 day of recommendation for the intervention group compared to the control group.

a. 0.65

b. -0.65

c. 6.4

d. 0.16

e. 24.1

f. 0.04

8.- Interpret the estimate from item #7in a sentence.

a. The absolute difference in proportions (probability) of getting vaccinated within 30 days for subjects in the intervention group compared to subjects in the control group is 24.1

b. The absolute difference in proportions (probability) of getting vaccinated within 30 days for subjects in the intervention group compared to subjects in the control group is -24.1

c. An individual who receives the intervention has a 2310% greater risk (24.1 times the probability) of being vaccinated within 30 days compared to if this individual was in the control group.

d. An individual who receives the intervention has a 2410% lower risk (-24.1times the probability) of being vaccinated within 30 days compared to if this individual was in the control group.

e. An individual who receives the intervention has a 2310% greater odds (24.1 times the odds) of being vaccinated within 30 days compared to if this individual was in the control group.

f. An individual who receives the intervention has a 2410% lower (-24.1 times the odds) odds of being vaccinated within 30 days compared to if this individual was in the control group.

9.- Do the estimated risk difference, relative risk and odds ratio agree in terms of the direction of association?

a. Yes

b. No

10.- How do the estimated relative risk and estimated odds ratios compare in value?

a. The two estimates are very similar in value.

b. The odds ratio is substantially greater than the relative risk.

c. The odds ratio is substantially less than the relative risk

11.- Suppose you were to mistakenly reportthe value of estimated odds ratio from item #7 as"the estimated relative risk"- in other words, if the valueyou got forthe odds ratio is XX, but you state "the relative risk of being vaccinated for the intervention group compared to the control group is XX". What would this do to the reported efficacy of the intervention program with regard to the vaccination outcome (under estimate or over estimate the efficacy)?

a. Under estimate the reported efficacy in terms of individual risk of getting the vaccine

b. Over estimate the reported efficacy in terms of individual risk of getting the vaccine

c. This would have little to no impact