Algebra 2 / Unit 10: Statistics and Data Analysis
10.5 Surveys, Observational Studies and Experiments
Notes
- Survey: ask people questions.
- Observational study: watch and record without changing anything. It can show an association but not cause and effect.
- Experiment: researchers apply a treatment to subjects. A randomized experiment with a control group can show cause and effect.
- Random assignment balances other factors between groups. A placebo is a fake treatment, so subjects don't know which group they're in.
Practice
Researchers randomly assign 100 volunteers to take either a vitamin or a placebo, then compare their colds. This is:
The researchers impose a treatment.
A study records students' sleep hours and grades and finds that students who sleep more get higher grades. What can be concluded?
It is an observational study, so other factors could explain the link.
Why do experiments use random assignment?
Randomizing spreads differences among subjects evenly across groups.
Ready for more? Take the Unit 10 test.