| Course | PHLT 8522 Epidemiological Investigations |
|---|---|
| Week | Week 5 |
| Paper type | Hypothesis memo |
| Length | About 930 words, 5 pages |
| Format | Memo, APA 7 citations |
| School | Walden University |
| Program | PhD in Public Health |
| Updated | October 2026 |
Free sample paper for PHLT 8522 Week 5
Memorandum
To: Outbreak Response Team, City-County Health Department
From: Epidemiology Fellow (PhD in Public Health student)
Date: Month Day, Year
Re: Working hypothesis on the source of the riverfront histoplasmosis cases, with falsifying predictions for it and for two alternatives
The Hypothesis in One Sentence
Spores of Histoplasma capsulatum, released when excavators broke up the upper floors of the Front Street warehouse between September 8 and 19, were carried east-northeast on prevailing winds and caused the outbreak.
Why This Hypothesis Comes First
Three pieces of the descriptive work point to it. The warehouse's upper floors held a pigeon roost for decades, according to the building inspector's condemnation report, and accumulations of bird droppings are the classic habitat for the fungus; birds, bats or droppings were present in 77% of outbreak settings reviewed by Benedict and Mody (2016). Demolition is among the most common settings for outbreaks in that review. The site lies at the western edge of the four blocks where most cases live or work, and airport records show winds from the west and southwest on most days of the demolition period. Finally, the onset curve implies a shared exposure lasting days, matching the length of the demolition. None of that is proof; each piece could also fit something else.
What Would Prove It Wrong
Platt (1964) urged scientists to name in advance the result that would end a hypothesis, and that discipline applies to a field investigation as much as to a laboratory. Three observations would count against the warehouse.
First: No Excess Time Downwind
If cases spent no more time outdoors in the area downwind of the site during September 8 to 19 than comparable people from the same part of the city, the hypothesis fails. The downwind area will be drawn from hourly wind records before any interviews begin, so that it cannot be shaped by where cases happen to live.
Second: Onsets Out of Step With the Work
If a meaningful share of cases had onset before September 11, too soon after the first demolition day for typical incubation, or had their only time in the district after September 25, too late to have breathed spores released by work that ended on September 19, the warehouse could not explain them.
Third: The Wrong Crew
Three cases work for the salvage and demolition company. If none of them worked at the Front Street site, and all three worked only at the company's other September jobs, their illness would point to another site and weaken the case for this one.
Rival One: Tree Trimming in Riverside Park
City crews removed limbs from a stand of trees used as a starling roost in Riverside Park on September 10 and 11, and mowed the guano-covered ground beneath. Starling roosts are a recognized habitat for the fungus. If the park is the source, cases should be concentrated among park users on or shortly after those two days, and because the disturbance lasted two days, onsets should fall within a narrower window, roughly September 16 to 27, than the three weeks observed. Residents of the northeast quarter, three blocks from the park, should be no more affected than other park neighbors.
Rival Two: Regrading of the Athletic Field
An athletic complex two kilometers north of the district was regraded from September 5 to 12. Soil disturbance alone can release spores where the fungus is established. If the field is the source, cases should include players, coaches and spectators, and residents north of the district should be affected at least as much as those within it. With winds mostly from the west and southwest, spores from the field would travel away from the district, not into it.
Table 1
Predictions for the Hypothesis and Its Rivals
| Observation | Warehouse | Park trimming | Field regrading | |
|---|---|---|---|
| Excess time near the source among cases | Downwind zone, September 8-19 | Park visits, September 10-14 | Field visits, September 5-12 | |
| Onset window | About September 15 to October 6 | About September 16 to 27 | About September 12 to 27 | |
| Who is affected | Downwind residents, workers and passersby, warehouse crew | Park users | Players, spectators, northern residents | |
| Wind needed | From west and southwest | Any, short range | From north | |
Note. Windows apply typical outbreak incubation periods (Benedict & Mody, 2016) to the dates of each activity.
How the Team Will Test Them
A case-control study will compare cases with controls from the same part of the city on three exposures, one per candidate source, measured with the same questions and the same time windows. Goodman et al. (1990) note that the analytic step in a field investigation tests hypotheses generated by description; here, it tests three at once so that no source is favored by the questionnaire. Work histories for the three company employees will be requested from the employer with their consent. Environmental sampling at the warehouse lot may be considered, but a negative sample would not clear the site, since detecting the fungus in soil and debris is difficult and, as Benedict and Mody (2016) note, would likely not change control recommendations.
A Note on Confirmation
If the case-control results support the warehouse, the strength of the conclusion will still depend on how well the three falsifying tests were run. A supportive result from a weak test would be worth little; a supportive result from a test that could plainly have failed is worth a great deal.
What the Team Should Not Do Yet
The warehouse should not be named publicly as the source until the case-control results are in, though precautions at active sites need not wait, and the next memo will address them.
References
Benedict, K., & Mody, R. K. (2016). Epidemiology of histoplasmosis outbreaks, United States, 1938-2013. Emerging Infectious Diseases, 22(3), 370-378. https://doi.org/10.3201/eid2203.151117
Goodman, R. A., Buehler, J. W., & Koplan, J. P. (1990). The epidemiologic field investigation: Science and judgment in public health practice. American Journal of Epidemiology, 132(1), 9-16. https://doi.org/10.1093/oxfordjournals.aje.a115647
Platt, J. R. (1964). Strong inference. Science, 146(3642), 347-353. https://doi.org/10.1126/science.146.3642.347
The Walden PHLT 8522 Week 5 instructions
Hypothesis weeks ask students to state the most likely explanation for an outbreak and to explain how it will be tested. Instructors look for a hypothesis specific enough to fail: an agent, a source, a route, a time and a population. Many prompts ask for alternative hypotheses and for the evidence that would distinguish among them. A strong submission uses the descriptive findings as the basis for each hypothesis and avoids treating the leading one as established. Memo format of two to three pages is common, often with a comparison table. Students are generally expected to describe the analytic study that will test the hypotheses and the role, if any, of laboratory or environmental evidence. Citations to the agent's epidemiology and to scientific reasoning are standard.
Inside the PHLT 8522 Week 5 example
The memo states the hypothesis in one sentence, then explains why it comes first using the roost, the setting, the wind and the curve, while noting each piece could fit something else. A section on falsification cites strong inference and gives three tests: excess time downwind, onsets in step with the work and the crew's work history. Two rival sections describe the park trimming and the field regrading with their own predictions. Table 1 compares all three on four observations, with windows derived from published incubation periods. A testing section describes a case-control study with one instrument for all three sources and explains the limits of environmental sampling. A final line says what the team should not yet do.
Where the marks sit in the PHLT 8522 Week 5 rubric
Hypothesis memos are scored on testability, fairness to alternatives and a clear plan. The sample's one-sentence hypothesis names mechanism, source, period and direction, which earns testability credit, and its three falsifying observations are concrete. Fairness credit comes from giving each rival a full set of predictions rather than a dismissive line. The comparison table shows the predictions side by side, which graders value for clarity. Planning credit comes from a single instrument for all three sources and a reasoned view of environmental sampling. Restraint about public naming earns a smaller share. Memo form, length and citations complete the scoring. Memos that state the leading source as fact, or offer rivals only as a formality, rarely reach the top band.
PHLT 8522 Week 5 help from the desk
Hypotheses are often too vague to test, such as "an environmental source in the district." Name the source, the route, the period and who should be affected. Then write down what would prove you wrong before you collect data. Give each alternative its own predictions and test them on equal terms. Use the descriptive findings to justify each hypothesis without overstating them. Explain how the analytic study will distinguish among the candidates. Be clear about what environmental or laboratory results can and cannot add. Avoid naming a source publicly before testing. A hypothesis memo for your own scenario can be prepared at no cost as a first sample.
Get a PHLT 8522 Week 5 example written to your instructions
Collect the descriptive findings your hypothesis must answer, then add the Week 5 prompt and rubric. The memo states one testable claim, lists the observations that would contradict it, and gives each rival explanation predictions as sharp as the favored one. First memo free, returned in 24-48 hours.
More PHLT 8522 papers and PhD in Public Health samples
- PHLT 8522 Week 1: Signal Appraisal Memo
- PHLT 8522 Week 2: Case Definition Brief
- PHLT 8522 Week 3: Case Finding Plan
- PHLT 8522 Week 4: Descriptive Summary
- PHLT 8522 Week 6: Peer Reply
- PHLT 8522 Week 7: Analytic Comparison
- PHLT 8522 Week 8: Decision Brief
- PHLT 8522 Week 9: Control Recommendation
- PHLT 8522 Week 10: Public Summary
- PHLT 8522 Week 11: Final Investigation Report
- PHLT 8520 Week 5: Selection Analysis
- PHLT 8500 Week 5: Outcome Type Brief
- PHLT 8450 Week 5: Asset Inventory
- PHLT 8331 Week 5: Two-Group Mean Comparison
PHLT 8522 Week 5 questions, answered
Where can I find a free PHLT 8522 Week 5 sample paper?
The full Week 5 hypothesis memo is published above, naming a demolition as the leading source, listing falsifying observations and testing two rivals, with a comparison table.
What makes an outbreak hypothesis testable?
It names a specific source, route, period and affected group, and it states in advance which observations would show it to be wrong.
Why test alternative sources at the same time?
Testing all candidates with the same questions and time windows means no source is favored by the instrument, so a difference between them is more convincing.
Can environmental sampling prove a histoplasmosis source?
Rarely on its own. Detecting the fungus in soil is difficult, a negative result does not clear a site and detection would likely not change control recommendations.
What is strong inference?
A method of scientific reasoning that sets out alternative hypotheses and designs tests whose outcomes would exclude one or more of them.