Chapter 2. Statistical Power and Underpowered Statistics
You’ve seen how it’s possible to miss real effects by not collecting enough data. You might miss a viable medicine or fail to notice an important side effect. So how do you know how much data to collect?
The concept of statistical power provides the answer. The power of a study is the probability that it will distinguish an effect of a certain size from pure luck. A study might easily detect a huge benefit from a medication, but detecting a subtle difference is much less likely.
The Power Curve
Suppose I’m convinced that my archnemesis has an unfair coin. Rather than getting heads half the time and tails half the time, it’s biased to give one outcome 60% of the time, allowing him to cheat at ...