Investigators wished to study whether pregnant women over the age of 42 were less likely to suffer from postnatal depression if they were paired up with mentors during and post pregnancy. The 121 women over the age of 42 in the study were paired up with mentors during the last trimester of pregnancy. All the women had their Edinburgh Postnatal Depression Scale implemented prior to giving birth (in week 38 gestation), and then at 12 weeks post gestation. You are interested in investigating if the difference in mean EPSD was significant. What kind of sample and outcome is this?