Final answer:
The harmonic mean of the required sample sizes for the coach's experiment is equal to the sample size.
Step-by-step explanation:
The harmonic mean of the sample sizes required to achieve a power of 0.80 for the coach's experiment can be calculated using the formula:
Harmonic mean = 2 / (1/n1 + 1/n2)
Where n1 and n2 are the sample sizes of the two groups being compared.
In this case, since only one effect size (d = 0.80) is given, we can assume that the sample sizes of the two groups are the same.
Substituting the given values into the formula:
Harmonic mean = 2 / (1/n + 1/n) = 2 / (2/n) = 2n/2 = n
Therefore, the harmonic mean of the required sample sizes is n.