魅影直播

Random assignment of experimental units to treatment groups is the most reliable way people know for constructing fair tests of treatments. But it is by no means perfect. We鈥檒l show you how varied the differences between groups can be simply due to random labelling.

(See also the Review Questions following the movie)

[]

After you鈥檝e watched this video, you should be able to answer these questions:

• What is randomisation variation and why is it a problem?
• How can we reduce the levels of randomisation variation?