NURS 832 Week 4 Discussion Board Forum 2 on Measures of Association and Study Design Example

Reviewed by Rachel Stanton, MSN, RN · Liberty University · Updated

In this NURS 832 Week 4 sample, a family nurse practitioner explains measures of association through a design patients never hear about: the test-negative case-control study that produces each season's flu vaccine effectiveness estimate. Using California's 2025-26 interim estimate, in which 22% of 86,369 people with positive flu tests and 27% of 866,396 with negative tests had been vaccinated, the thread calculates a crude odds ratio of 0.76 by hand, shows why the published adjusted effectiveness of 33% differs, and weighs the design's strengths and biases with a meta-analysis of 165 studies. In Liberty University NURS 832, where DNP students learn epidemiology and statistics for prevention, this forum carries 100 points in Module/Week 4. The reply applies the same reasoning to odds ratios from a cross-sectional study of measles immunity.

CourseNURS 832 Clinical Prevention and Biostatistics (NURS832)
Module/Week4
AssignmentDiscussion Board Forum 2 on Measures of Association and Study Design
Paper typeDiscussion thread with one reply
Lengthabout 536 words (thread and replies). Course guide: a thread in response to the forum topic citing two peer-reviewed journal articles, and a reply to one classmate citing one different article, in graduate-level writing and current APA, with no required word count
FormatAPA 7 citations and reference list
Points100
SchoolLiberty University Online
ProgramDNP
Where it sitsModule/Week 4 in Liberty's published NURS 832 course guide; current sections can differ
UpdatedOctober 2026

Free sample paper for NURS 832 Week 4

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Discussion Board Forum 2: Reading an Odds Ratio Backward Into Vaccine Effectiveness

NURS 832 Clinical Prevention and Biostatistics, Discussion Board Forum 2

Thread by [Student Name]

The clinic and the classmate replied to are composites written for a model discussion; the studies cited are real, and the crude odds ratio is the student's own calculation from the published percentages.

Why this part earns its pointsRebuilding the two-by-two table from published percentages shows the classmates exactly where a familiar number comes from.
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"So the flu shot only works a third of the time?" A patient asked me that after reading a news story about this season's vaccine. The question is reasonable, and answering it means explaining both a study design and a measure of association.

Vaccine effectiveness is rarely measured in randomized trials once a vaccine is recommended, so health departments use observational designs. The most common is the test-negative case-control design. Among people tested for influenza, those who test positive are cases and those who test negative are controls, and the investigators compare the odds of vaccination in the two groups. Because case-control studies sample by outcome, they cannot estimate incidence or relative risk directly; the measure of association is the odds ratio (Macha & McDonough, 2012).

California's interim estimate for 2025-26 is a good example. Of 952,765 influenza tests reported from October 2025 through January 2026, 86,369 were positive and 866,396 negative; 22% of case-patients and 27% of control patients had been vaccinated, and interim vaccine effectiveness against any influenza was 33% (Zhu et al., 2026). From the percentages, I rebuilt the crude two-by-two table:

VaccinatedUnvaccinatedOdds of vaccination
Cases (positive)22%78%0.282
Controls (negative)27%73%0.370

The crude odds ratio is 0.282 divided by 0.370, or 0.76, and crude vaccine effectiveness is one minus the odds ratio, or about 24%. The published 33% comes from the authors' statistical model rather than the raw percentages; test-negative analyses typically adjust for factors such as age and calendar time, which differ between vaccinated and unvaccinated people and can move the estimate in either direction. The patient hears 33%, but the study measured odds, and the odds were adjusted; each step is a choice someone made.

The design's strength is that everyone in it sought care and was tested, which reduces bias from differences in health-care-seeking behavior. Its weaknesses include misclassification of vaccination status and confounding by factors linked to both vaccination and infection. Effectiveness is also higher against severe outcomes than against any infection: a meta-analysis of 165 test-negative studies found pooled effectiveness of 42% against influenza-associated hospitalization, 52% against intensive care admission and 55% against ventilatory support, with higher estimates in children and in well-matched seasons, although certainty was low to very low (Yegorov et al., 2026). So my answer to the patient was that the vaccine reduces the chance of testing positive by about a third this season, and reduces the chance of the worst outcomes by more.

Why this part earns its pointsThe reply picks up a different design and measure, which widens the discussion instead of repeating the thread.
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Reply to Devin

Devin, your post on cross-sectional studies raised a good point about odds ratios. A cross-sectional study can estimate prevalence directly, so a prevalence ratio is often the better measure, but many studies report odds ratios from logistic regression. A recent study of 16,446 veterans tested for measles immunity during the 2025 West Texas outbreak found 9.18% were seronegative and reported odds ratios for seronegativity of 5.65 for veterans aged 64 or younger, 3.54 for Janus kinase inhibitor use and 3.10 for an immunodeficient condition (Gentry et al., 2026). Because seronegativity was under 10%, those odds ratios approximate prevalence ratios, though the largest one somewhat overstates the relative prevalence. The age finding also makes sense historically: people born before 1957 are generally presumed immune from natural infection. Would the authors' conclusions change if the outcome had been common, say 40% seronegative?

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References

Gentry, C. A., Kurdgelashvili, G., & Scofield, R. H. (2026). Characterizing measles IgG-related seroprevalence in the US veteran population during the 2025 West Texas outbreak. American Journal of Infection Control. Advance online publication. https://doi.org/10.1016/j.ajic.2026.08.004

Macha, K., & McDonough, J. P. (2012). Epidemiology for advanced nursing practice. Jones & Bartlett Learning.

Yegorov, S., Patel, O. D., Sharma, H., Khan, T., Gupta, R., Yao, M., Sritharan, A., Silverman, N., Pullenayegum, E., Miller, M. S., & Loeb, M. (2026). Effectiveness of influenza vaccination to prevent severe disease: A systematic review and meta-analysis of test-negative design studies. Clinical Microbiology and Infection, 32(2), 219-229. https://doi.org/10.1016/j.cmi.2025.09.023

Zhu, S., Quint, J., León, T. M., Li, N. J., Muldrew, S., Porse, C., Flannery, B., Ellington, S., Murray, E. L., Sachdev, D., McCullough, K., & Schechter, R. (2026). Interim estimates of 2025-26 seasonal influenza vaccine effectiveness: California, October 2025-January 2026. Morbidity and Mortality Weekly Report, 75(9), 124-128. https://doi.org/10.15585/mmwr.mm7509a3

What the NURS 832 Week 4 instructions ask

The second NURS 832 forum comes in Module/Week 4, alongside Macha and McDonough's chapters on epidemiologic study designs and on measures of association and causation. The course guide's rules match Forum 1: a thread on the assigned topic showing course knowledge in depth and breadth, two peer-reviewed journal articles cited in the thread, one different peer-reviewed article in the single reply, graduate-level writing in current APA and no required length. The most useful threads, as in the first forum, take a published result and show where its numbers come from, so classmates can see how a study design produces its measure of association.

How this NURS 832 Week 4 example is built

The thread begins with a patient's question about why the flu shot is called only one-third effective. It explains why vaccine effectiveness studies use case-control designs, defines the odds ratio and shows a two-by-two calculation using the percentages from California's interim estimate. It explains how vaccine effectiveness is derived from the odds ratio and why an adjusted estimate can differ from a crude one, then discusses the test-negative design's built-in control for health-care-seeking behavior and its remaining biases, with pooled estimates against severe outcomes. In the reply, a classmate's cross-sectional example becomes the occasion for explaining when an odds ratio approximates a prevalence ratio.

NURS 832 Week 4 grading rubric: where the points go

Forum 2 uses the same yardstick as Forum 1: correct epidemiology, a discussion that goes deep and wide, the required pair of journal articles in the thread plus a third in the reply, graduate-level writing and APA. For a measures-of-association topic, instructors look for correct matching of design to measure, case-control studies to odds ratios and cohort studies to relative risks, a correct calculation and an interpretation that a patient could understand. Recognizing the design's biases, rather than only its result, shows critical reading. A reply that moves to another design, such as a cross-sectional or cohort study, demonstrates that the student can match measures to designs beyond the one in the thread, and a closing question to the classmate keeps the exchange going.

NURS 832 Week 4 help: mistakes that cost points

Threads on study design often recite the hierarchy of evidence and define each design without showing how any of them produces a number. Choose one published estimate you care about, rebuild its two-by-two table from the reported percentages and interpret it. Then ask what could make the estimate wrong: confounding, selection or misclassification. Keep the reply on a different study design or measure so that it widens the discussion, and use its single source well rather than adding several thin ones. If you report an adjusted estimate, say so, and if you calculate a crude one yourself, say that too, so readers know which number is which and why they differ.

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NURS 832 Week 4 questions, answered

What is NURS 832 Discussion Board Forum 2?

The course's second forum, a 100-point Module/Week 4 discussion of study designs and measures of association, citing two articles in the thread and a third, different one in the reply.

Where can I find a free NURS 832 Week 4 sample paper?

The complete NURS 832 Week 4 thread on odds ratios and flu vaccine effectiveness, including the two-by-two calculation, the reply and the references, is on this page at no cost.

How is vaccine effectiveness calculated from an odds ratio?

In a case-control or test-negative study, vaccine effectiveness equals one minus the odds ratio of vaccination among cases versus controls, multiplied by 100, usually after adjustment.

What is a test-negative design?

A case-control design in which people tested for a disease are compared: those testing positive are cases and those testing negative are controls, which helps balance health-care-seeking behavior.

When does an odds ratio approximate a relative risk?

When the outcome is uncommon, roughly under 10%, the odds ratio is close to the relative risk or prevalence ratio; when the outcome is common, the odds ratio exaggerates the association.

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