SAME SEATS!!! You will be able to choose an SRS using a table of random digits and using technology....

SAME SEATS!!!

You will be able to choose an SRS using a table of random digits and using technology.

Today’s Objectives:

SRS

Simple random samples gives each individual an equal chance to be chosen. Names in a hat.

What about a SRS of the country’s 117 million households. Could we put that many slips of paper in a huge hat?

Random Digits

A table of random digits is a long string of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 with these two properties:

1. Each entry in the table is equally likely to be any of the 10 digits.

2. The entries are independent of each other.

Look at Table B in the back of your book.

Table B

To make the table easier to read, the digits appear in groups of five and in numbered rows.

The groups and row numbers have no meaning.

Turn to pg. 207

Choose an SRS From Table B

Step 1: LabelAssign a numerical label to every individual in the population. Be sure that all labels have the same number of digits.

Step 2: TableUse random digits to select labels at random

Practice

In your notes or on a new sheet of paper…

Write down exactly how YOU would use Table B to select a simple random sample of 3 students from our class.

Critique

Critique each plan, with emphasis on… 1. The correspondence between random

digits and individuals in the class (Label), and

2. The mechanics of using the table of random digits (Table).

Extension

Get out a clean sheet of paper. Write your name at the top.

Fully describe (in writing) a plan for obtaining a simple random sample of 3 students from our school using an alphabetical roster. Explain how you would label the students and how you would use the table.

Hints Table B

1. You can assign labels in any convenient manner such as alphabetical.

2. Use the shortest possible labels for the number of individuals in the population.

3. It is good practice to begin with 1 or 01 or 001, as needed.

4. As a standard practice read across the rows, not down.

Computer-Generated Digits

Computer software can choose an SRS.

1. Get out one sheet of paper per group and something to write with.

2. Stay with your group.

3. When you are told you need to take a statistics book with you as you move to your assigned computers.

4. Work through the Activity 5.1B on pg. 211

5. Once you have finished questions 1-6 please see me to get the extension activity.

Homework

Pg. 216-217 #’s 5.13, 5.18, 5.19, 5.22

Due Monday!