The statistical analysis aimed to estimate the effect
of gender, diagnosis and age on postoperative bleeding;
it was performed using a logistic regression.
Gender, diagnosis and type of operation are factor
variables with 2, 8 and 2 levels, respectively, while age
was measured as an integer variable with values in the
interval 0 to 89 years of age. Thus, the factor variable
‘gender’ with two levels means that gender can have
one of two values.