Cocoa plant type 1 yielded 155 bushels per acre last year at a research farm. This year,
cocoa plant type 2, planted in the same location, yielded only 123 bushels per acre and
there was a major freeze. The researchers do not know whether the difference is the
result of the superiority of type 1 or the freeze. What is this an example of? (4 points)
- Bias
- Confounding variable
- Matched-pairs desighs
- The placebo effect
- Replication