PHLT 8522, Week 7: in this analytic comparison example, cases and controls compared on time downwind give an illustrative odds ratio of 6 for Tower A, with both rivals flat. Searches like "phlt 8522 week 7 assignment example", "phlt8522 week 7 sample" and "phlt 8522 week 7 example" land here.
What a finished PHLT 8522 Week 7 analytic comparison looks like
About four pages hold methods, one results table and a discussion. Methods describe how controls were found: three per case, drawn by address-based sampling from the same blocks, with workplace controls taken from the same employers for commuting cases. Exposure is defined as any time outdoors inside the pre-drawn downwind zone during the exposure period. The results table, every count illustrative, shows 12 of 16 cases and 16 of 48 controls reporting time in Tower A's zone, an odds ratio of 6, while Tower B's zone and the fountain plaza show near-equal proportions in both groups. Its discussion reads the pattern, notes that two cases could not be interviewed, and names differences in how cases and controls recall their movements as the leading remaining concern.
How a PHLT 8522 Week 7 example is structured
Methods lead so the reader judges the controls before seeing any result, since a case-control comparison stands or falls on its answer to who would have been counted had they fallen ill. Controls come from the same blocks and employers as cases for that reason. The exposure definition is the document's most important sentence: the downwind zone was drawn from wind records before interviews began, which guards against drawing the target around the cases after the fact, the error often called the Texas sharpshooter fallacy. The results sit in one table, all three candidate sources side by side, so the rivals are tested by the same rule. The discussion reads the odds ratio as strong support for Tower A without calling it proof, then ranks the remaining concerns, recall first and missing interviews second.
Controls from the same blocks
Three per case come from the same neighborhoods and employers, answering who would have been counted had they fallen ill.
A zone drawn in advance
Wind records fixed the downwind boundary before interviews, so the target was not drawn around the cases.
Three sources, one table
Tower A, Tower B and the fountain plaza are compared on identical terms, all counts illustrative.
Twelve of sixteen against sixteen of forty-eight
Time in Tower A's zone gives an odds ratio of 6, while both rivals show near-equal proportions.
What the comparison leaves open
Recall differences and two uninterviewed cases are ranked as the remaining concerns.
Where marks go in PHLT 8522 Week 7
An analytic comparison is only worth marks if its result could have come out otherwise; this one fixed its exposure zone before any interview so that it could. The pre-drawn zone earns the largest credit, since defining exposure after seeing the case map is the commonest way such comparisons mislead. Control selection draws a substantial block: sampling from the same blocks and employers shows the author understands whom controls must represent. Testing rivals by one rule is rewarded as fairness. The odds ratio collects accuracy credit when read as strong support, not proof. Ranking recall and missing interviews as remaining concerns earns the judgment share. Comparisons drift downward when controls come from a convenient list, when the zone is drawn around the cases, or when a large odds ratio is announced as the source.
Get a PHLT 8522 Week 7 example written to your instructions
Case data, control information or the scenario under analysis belongs alongside the Week 7 prompt and rubric. The comparison defines exposure before looking, tests every candidate source by the same rule, and reads the result at the strength the design supports. A first comparison is free, back within 24-48 hours.
PHLT 8522 Week 7 questions, answered
What is the Texas sharpshooter fallacy?
The error of firing at a barn and then painting a target around the tightest cluster of holes. In an investigation, it means drawing an exposure zone around where cases happen to be and then finding that cases were exposed. The comparison avoids it by fixing the downwind zone from wind records before interviews began. A custom comparison states when and how exposure was defined in your scenario.
Why use neighborhood controls instead of hospital patients?
Because controls should represent the people who would have become cases had they been infected, and in this event that means people who live, work or spend time in the same district. Hospital patients come from wherever the hospital draws them and may differ in how often they go downtown. The example samples addresses and employers for that reason. A custom comparison chooses controls to fit your event's source population.
Is an odds ratio of 6 proof that Tower A was the source?
No. It is strong support from a design that can still be distorted, most plausibly by cases recalling their movements differently than controls. The number is invented for the page and labeled illustrative. Legionnaires' investigations usually combine epidemiologic, environmental and laboratory evidence before naming a source, and the composite report waits for all three. Your own comparison should report its result at the strength the evidence allows.