'Calculate the power of a F-test for one factor ANOVA.
Parameters
effect_size : float
standardized effect size, mean divided by the standard deviation.
effect size has to be positive.
nobs : int or float
sample size, number of observations.
alpha : float in interval (0,1)
significance level, e.g. 0.05, is the probability of a type I
error, that is wrong rejections if the Null Hypothesis is true.
k_groups : int or float
number of groups in the ANOVA or k-sample comparison. Default is 2.
Returns
power : float
Power of the test, e.g. 0.8, is one minus the probability of a
type II error. Power is the probability that the test correctly
rejects the Null Hypothesis if the Alternative Hypothesis is true.'

def power(self, effect_size, nobs, alpha, k_groups=2):

    return ftest_anova_power(effect_size, nobs, alpha, k_groups=k_groups)
