For each of the following scenarios, identify which sampling method is used:
a. The State College is conducting a survey of student attitudes and opinions. The plan is to use the list of all registered students and then select every 10th name on the list to make up the sample. 

b. The city population consists of four major ethnic groups. A researcher studying resident attitudes concerning a proposed city park surveys a large number of city residents and then selects the first 30 responders from each ethnic group to make up the sample.
c. A second option for the survey in Part b is based on the observation that the four ethnic groups are not represented equally in the population. To ensure that the sample reflects these differences, the researcher first determines the number of residents in each ethnic group and then selects a sample so that the number for each group in the sample is in direct relation to the number in each group for the entire city population.
d. The County Democratic Committee would like to determine which issues are most important to registered Democrats in the county. Starting with a list of registered Democrats, the committee uses a random process to select a sample of 30 names for telephone interviews.
e. A medical research laboratory places ads in the local newspaper to recruit people with chronic migraine headaches to participate in clinical trials evaluating a new medication. Qualified individuals are asked to phone the lab for a screening appointment.