Four interrelated features of power can be summarized using BEAN
|B||Beta Error (Power = 1 – Beta Error): Beta error (or Type II error) is the probability that a test of statistical significance will fail to reject the null hypothesis when it is false (e.g., when there really is an effect of training).
|E||Effect Size: The effect size is the magnitude of the difference between the actual population mean and the null hypothesized mean (μ1 – μ0) relative to standard deviation of scores (σ). When the effect size d = (μ1 – μ0) / σ in the population is larger, the null and population sampling distributions overlap less and power is greater.
|A||Alpha error: Alpha error (or Type I error) is the probability that a statistical test will produce a statistically significant finding when the null hypothesis is true (e.g., there is no effect of training). For example, if alpha error = .05 and the null hypothesis is true, then out of 100 statistical tests, false significance would be found on average 5 times. The risk of false significance would be 5%. In practice, alpha is typically set by the researcher at .01 or .05
|N||Sample Size: As the sample size increases, the variability of sample means decreases. The population and null sampling distributions become narrower, overlapping to a lesser extent and making it easier to detect a difference between these distributions. This results in greater power.
Select true or false for each scenario:
|(Assuming no other changes)||True||False|
|1. As effect size increases, power decreases.|
|2. As sample size increases, power increases.|
|3. As alpha error increases, power decreases.|
|4. Beta error is unrelated to power.|
Check your answers:
1. Click for answer
False; as effect size increases, power increases.
2. Click for answer
True; as sample size increases, power increases.
3. Click for answer
False; as alpha error increases, power increases.
4. Click for answer
False; beta error = 1 – power.
In this tutorial, we will discuss each component of the B.E.A.N. mnemonic in greater detail.
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