Practice Experimental Design in Statistics
Use these practice problems to test your method after reviewing the concept explanation and worked examples.
Quick Recap
The careful planning of experiments to establish cause-and-effect relationships by controlling variables and using comparison groups.
Want to know if a new fertilizer helps plants grow? You can't just use it on some plants and see if they grow - maybe they would've grown anyway! You need identical plants, give fertilizer to some (treatment) but not others (control), and keep everything else the same.
Example 1
easyA farmer wants to test whether a new fertiliser improves crop yield. She applies the new fertiliser to Field A and uses the old fertiliser on Field B. She finds Field A produces more. Can she conclude the new fertiliser is better? Identify the flaw in the experiment.
Example 2
mediumDescribe the key components of a well-designed experiment to test whether a new study method improves exam scores. Include: treatment and control groups, random assignment, and what should be kept constant.
Example 3
mediumA doctor tests a new headache medicine. She gives the medicine to patients who ask for it and compares their recovery to patients who didn't ask. Identify at least two problems with this experimental design.
Example 4
hardDesign a double-blind experiment to test whether caffeine improves reaction time. Specify: (a) how participants are assigned, (b) what the treatment and control conditions are, (c) what 'double-blind' means and why it matters, (d) the response variable.