Sample size
The mean score for the PSS-10 was found to be 18.3,
with a standard deviation of 4.9 in the validation study
among postpartum women in Lebanon [13]. Sample size
was calculated based on the aim of reducing the PSS-10
mean by 4 points. Assuming that 50% of women in the
intervention arm would watch the film, the mean for the
intervention group was considered to be 16.3. Therefore,
126 women were needed in each arm with an alpha of
0.05 and a power of 90%. A total of 140 women was
needed for each arm to allow for 10% loss to follow up.