What do we call the probability sampling in which the researcher randomly selects a subset of participants from a population?

What do we call probability sampling method in which sample members from a larger population are selected according to a random starting point but with a fixed, periodic interval?

What do we call a sample that is drawn from a number of separate strata of the population, rather than at random from the whole population, in order that it should be representative?

What type of sampling occurs when researchers divide a population into smaller groups, then randomly select among these groups to form a sample?

You want to gain data about the standardized test scores for all the fifth graders in your county. You have access to lists of fifth graders at other local schools and decide to sample randomly from groups of these fifth graders. What type of sampling did you use?

You want to survey some local people about changes to the county's transit system. You spend the day at a nearby movie theatre, and survey the people who are leaving. What type of sampling was this?

You are going to poll a sample of students at your school about their views on recess. You put all 300 students' names into a hat, and pull out 30 of them to survey. What type of sampling is this?

A political pollster wants to survey the population in your state on how they will vote in the next election. They take a list of all the registered voters and send the survey to every fifth person on the list. What kind of sampling is this?

What kind of sampling are we using if we first divide our population into groups based upon some factor like age, gender, or voting preference?