Random Sampling Methods

Every possible group of units of the required size has the same chance of being the selected sample as any other sample of the same size.

This sample is selected by dividing the population into subgroups and then taking a fixed number of units from each group using the simple random sample.

Identify the sampling design: Student government randomly samples 25 students of each of the four classes.

Identify the sampling design: Mr. Rhoades puts all of his students' names in a hat and randomly selects one without looking.

Interview every 10th student who enters the school in the morning.

A teacher wants to know how well her students are doing on a topic. She randomly picks one class to survey.

Units of the population are grouped; one or more groups are selected at random.  All units of that group are included in the sample.

Identify the sampling design: The LFCC registrar wants to investigate attitudes of their graduates.  The registrar randomly selects 100 names from each of the four past graduating classes.

The names of 70 contestants are written on 70 cards. The cards are placed in a bag and three names are picked from the bag.

You are interested in finding out the percent of residents in the city that have experienced a robbery in the past year. Using the city property records, you assign each residence a number. You use a random number generator to give you a list of numbers. You contact the residence that corresponds to that number to ask your questions.