A small university in North Carolina takes a poll to find out what students think of the service at the University's Wellness center. 500 students are randomly chosen to answer the poll questions. The response rate was 100%. The population is A university has 2000 male and 1000 female faculty members. The Human Resources department is commissioning a survey on childcare, and wants to sample 150 faculty members, including an SRS of 100 male members and an SRS of 50 female members. What kind of sampling method is this