What to do…  1.Share with your group the 5 questions that you have written about what you would ask other students regarding their opinions about having a closed campus.

Next…  2.What type of questions were there: How many had yes/no? How many had open response? How many had a multiple choice? How many had a combination? Write this on a paper, to be turned in. Identify by name who had what type of questions.

Finally…  3.What do you consider the most biased question on each student’s paper? Why? Write your opinion(s) on the paper you have started. Remember to back up your opinion(s). Don’t forget to label the owner of each of the questions.

And now on to some notes

First, the BAD ones…  1.Voluntary Response Sampling This is when you are surveying through write-in polls, call-in polls, or the internet, and anyone can respond if they want to. Usually the people who respond are those with strong opinions about the topic. This creates bias.

BAD, BAD, BAD…  2.Convenience Sampling This is when you ask people who are the easiest to contact (i.e., people in your class, people outside a grocery store, etc.) Again, because this sample is of individuals who are not randomly chosen, bias can occur. Even if you randomly choose from the grocery store who to ask, they are all from the same small group of people with a very specific trait in common.

But what’s good about those? They’re very easy to do and you can get fast results.

Now, the BEST one…  1. Simple Random Sample (SRS) All members of a group (the students of a school, for example) each have a identifying number (it can be their student id number or just a number like 1, 2, 3, …) and the number of students are chosen randomly from those identifying numbers to form a sample. Everyone will have an equal chance of being in the sample since they are being chosen randomly. What could be bad here?

This is what’s wrong with SRS’s  More people from one group, say the Seniors, can be chosen than the Freshman.  This is the chance you take with an SRS.  This can create bias, even if it wasn’t intended. It creates what is called UNDER COVERAGE

QUESTION FOR YOU…  Of the three types of sampling I have just introduced you to, what type of sampling method would asking the 5 question survey to your friends in the class be?

Upcoming events…  There are several other sampling methods we will be discussing during this chapter… Stratified Random Sample Cluster Sample Systematic Sample  Some are better than others. All of them have their good and bad points…more to follow.

Just so you know…  This is just a brief glimpse into these topics…there is MUCH more to all of these topics that we will be talking about as the chapter goes on.

Important info…  Friday we will be using the Table of Random Digits in the back of your books and learning some functions on your graphing calculators to generate random numbers.  PLEASE BRING YOUR BOOKS AND GRAPHING CALCULATORS!!!!

HOMEWORK #6  Page 67-68, #  Page 74-75, #