diffs = []
for i in range(n_replicas):
 sample = families.sample(frac=1.0, replace=True)
 male_sample_mean = sample[sample.gender == 'male'].childHeight.mean()
 female_sample_mean = sample[sample.gender == 'female'].childHeight.mean()
 diffs.append(male_sample_mean - female_sample_mean)
diffs = pd.Series(diffs)