Debrief AQR Have homework questions ready.

Things to think about… In statistics “random” means that some sort of system was used for selection Randomization (The method you used to select your samples) Random is not—stand in front of class saying, “You, you and you—I pick those three students.”

Things to think about… What do you mean by “The population of Spud Potato Chips” that you test? What factors must be considered when selecting a sample? Would it be possible to test bags of chips from around the world? What is it called when you can?

Things to think about… Census Definition: A census is a study in which every member of a population of interest is a participant. This may seem like the most accurate way to get information about a population but it has many problems:

Problems with census… A census can be very expensive A census can be almost impossible to accomplish A census may take so long to accomplish that the information becomes dated and accuracy is affected The study can destroy the subject (for example: vehicle safety crash tests

Randomization Card Match Split into pairs Directions: Match up one definition and one example per title of sampling technique. Write your answers in your book.

And the answers are… Simple Random Sampling Definition: The researcher chooses the sample from the entire population through a randomization technique Example: Drawing names out of a hat or using a random number table or random number generator

And the answers are… Stratified Random Sampling Definition: The researcher separates the population into a number of strata (statistical subpopulations) and then takes a random sample within each stratum Example: Freshmen, Sophomore, Junior and senior classes or males and females

And the answers are… Systematic Sampling Definition: The researcher separates the population into evenly sized groups, randomly selects one participant in the first group, and then selects every nth participant Example: The entire student roster is numbered, numbers 1 – 25 are placed in a hat, and a number is drawn. Say number 7 is chosen, every 25th student afterwards us selected

And the answers are… Cluster Sampling Definition: The researcher separates the population into groups and then randomly selects some of these groups to participate. Example: the numbers of every classroom in the school are placed in a hat, and five classrooms are selected. Every student in those five classrooms participates

And the answers are… Convenience Sampling Definition: The researcher selects participants based on easy accessibility Example: The researcher stands in one location at school and selects the first 50 students who walk by

Sampling… Recall the Spud Potato Chips scenario. You hypothesized that the true mean weight of the bags of chips might be less than the 28.3 grams as advertised. Discuss and make notes on how you might collect a sample of bags to test your hypothesis. Remember, the sample must be representative of the population.

Apply to Project… How do you get a random sample for your project. You must create a method Use one or more from the list you created in your book. Step 2 of project (Create your design)