Learning objectives
By the end of this lesson, you can:
- Name the main study types.
- Explain why an animal result does not prove a result in people.
- Explain why chance assignment and comparison groups help.
- Tell the difference between a statistical result and a useful benefit.
Ask what the design can establish
Different study types answer different questions. Lab studies test ideas in cells or samples. Animal studies test early effects in living animals.
A case report describes what happened to one person or a few people. An observational study looks for patterns without assigning treatments.
A randomized trial assigns people to groups by chance. It can give stronger evidence about cause and effect. A systematic review compares many studies using a set method.
Do not ask only, “Is there a study?” Ask, “What can this type of study show about this exact claim?”
Population, comparison, outcome, time
Start with the population: who or what was studied? Results in cells, mice, and people are not the same.
Next, check the comparison group. People may improve over time for many reasons. A fair comparison helps separate the treatment from those other reasons.
Randomization means assigning people to groups by chance. Blinding means hiding the group assignment from some people in the study. Both can reduce unfair influence.
Check the outcome, or what the study measured. Ask whether it matters to patients and whether the study lasted long enough.
Read benefits, harmful effects, missing information, and people who left the study together.
A statistical result may not be a useful benefit
“Statistically significant” means the result passed a set math test. It does not mean the change was large, useful, fair, or certain.
Record the actual difference between groups. Then ask whether the size and length of the effect fit the public claim.
Work through a claim mismatch
Imagine a study tested a cream on mice for seven days. The mice had a small change in one lab measurement.
An ad then says, “This injection heals sports injuries in people.” The product, route, population, outcome, and claim size do not match the study.
Compare the claim with what the study actually tested. Name each difference instead of treating the study as a simple yes-or-no answer.
Keep these
Lesson takeaways
- Different study types answer different questions.
- Read who was studied, the comparison, result, length, harms, and missing information together.
- Match the study details to the public claim.
Workbook action
Put the lesson to work.
Choose an evidence type for one source. Then write one sentence it supports and one sentence it does not support.
Knowledge check
Check what you can explain.
Answer all 3 questions. Get at least 2 correct to complete this module. You can retake the check after any result.