Is the Association Real, or Just Chance?
Experimental Design domain · Lesson 7 of 20 · Biomedical Innovations (BI)
Today's goal: Students will interpret an odds ratio, a p-value, and a 95 percent confidence interval, and decide whether an association is statistically significant.
What a finished product looks like
This is a model of the work you should turn in. Use it to check your own: match the structure and the level of detail, do not copy it. Your wording should be your own.
Significance sort (instructor practice values):
- Variant A: OR 2.1, 95 percent CI 1.3 to 3.4, p = 0.002. SIGNIFICANT: the CI excludes 1.0 and the p-value is well below 0.05.
- Variant B: OR 1.4, 95 percent CI 0.9 to 2.2, p = 0.11. NOT SIGNIFICANT: the CI includes 1.0 and p is above 0.05, so no effect is still plausible.
- Technique C: risk ratio 0.62, 95 percent CI 0.40 to 0.96, p = 0.03. SIGNIFICANT: the CI excludes 1.0 and p is below 0.05.
Largest effect size: Variant A has the largest point estimate (OR 2.1), but the largest effect is not automatically the most trustworthy. Trust depends on the confidence interval and p-value, not the point estimate alone; a big OR with a wide CI that crosses 1.0 would not be believable.
Also due today: Draw a number line with 1.0 marked and place each interval on it to check whether it crosses.
How this was built, step by step
The finished product above did not appear all at once. Here is the path from the question to the turned-in work, so you can follow the same steps.
- 1Start from today's question: How do we know an association is real and not just chance?
- 2Work the Model and the Explore questions to reason it out before writing anything.
- 3Pull the specific evidence the product needs from the reading and any database you used.
- 4Write it up in the required format: Sort three practice findings into significant or not significant with one sentence each (Variant A: OR 2.1, 95 percent CI 1.3 to 3.4, p = 0.002; Variant B: OR 1.4, 95 percent CI 0.9 to 2.2, p = 0.11; Technique C: 0.62, 95 percent CI 0.40 to 0.96, p = 0.03), then state whether the largest effect size is automatically the most trustworthy.
- 5Check it against the rubric, then submit.
| Criterion | Proficient | Developing | Beginning |
|---|---|---|---|
| Complete | Every required part of the artifact is present and filled in. | Most parts are present, but one is missing or left blank. | Several parts are missing. |
| Accurate | The science and data are correct and match the evidence. | Mostly correct, with a small factual slip. | Key science or data is wrong. |
| Scientific reasoning (CER) | States a claim, backs it with specific evidence, and explains the reasoning. | Has a claim and evidence, but the reasoning is thin or missing. | Gives an answer with no evidence or reasoning. |
| Professional communication | Clear, organized, and labeled the way a clinician or scientist would write it. | Readable but disorganized or missing labels. | Hard to follow. |
| Submitted | Turned in the right way (Schoology for routine work) and confirmed. | Turned in, but in the wrong place or unconfirmed. | Not turned in. |
- CompleteProficient: Nothing is left blank: the model fills every part of "Sort three practice findings into significant or not significant with one sentence each (Variant A: OR 2.1, 95 percent CI 1.3 to 3.4, p = 0.002; Variant B: OR 1.4, 95 percent CI 0.9 to 2.2, p = 0.11; Technique C: risk ratio 0.62, 95 percent CI 0.40 to 0.96, p = 0.03), then state whether the largest effect size is automatically the most trustworthy.".
- AccurateProficient: Every number and claim matches the case evidence.
- Scientific reasoning (CER)Proficient: It names a claim, cites the specific evidence, and explains the reasoning, not just the answer.
- Professional communicationProficient: It is organized and labeled like a real chart note.
- SubmittedProficient: It would be turned in on Schoology and confirmed.
WebXam problem for today's skill
One exam-style question that uses exactly what you practiced today. Try it before you reveal the answer, then read why each choice is right or wrong.
Tap an answer to see the full explanation. Nothing is recorded or graded.