1.2 – Random Samples

• Simple Random Sample– Every sample of size n from the population has an

equal chance of being selected– Every member of the population has an equal

chance of being included in the sample

Guided Exercise #3

• With table partners, turn to page 12– Cover answers– Discuss answers• Check

– Whole group clarification

How to draw a random sample

1. Number all members of the population sequentially

2. Use a table, calculator, or computer to select random numbers from the numbers assigned to the population members

3. Create the sample by using population members with numbers corresponding to those randomly selected

Random Number Table

• Look in the back of book: A1

Random Numbers

• Would you always want to start in upper left ?

• How would you generate a random sample of 30 cars out of 500 cars?

• Is picking every 5th car a random sample?

• How could we select a group of 10 numbers out of the numbers 20-80?

• How could we pick a group of 13 members from 1-10?

Simulations• Simulation:

• How could you use the random number chart to simulate something with 2 choices?– Heads/tails, rising/falling stocks, True/False

• Is tossing a coin a random way to generate a– 2 choice event?– 4 choice event?

• Is rolling a die a random way to generate a– 6 choice event?– 2 choice event?

A fair race?

• Flip the coin. If the coin lands on heads, the cat will advance one space. If the arrow lands on tails, the dog will advance one space. The first animal to reach the last circle is the winner.

O O O O O O O O O O

O O O O O O O O O O

Guided Exercise #4

• With table partners, turn to page 14– Cover answers– Discuss answers• Check

– Whole group clarification

Sampling Techniques

• Sampling with replacement

• Random:• Stratified:• Systematic:• Cluster:• Convenience:

Checkpoint

Explain the importance of random samples

Construct a simple random sample using random numbers

Simulate a random process

Describe stratified, cluster, systematic, and convenience sampling.

Homework

• Read Pages 11-16– Take notes on what we have not covered

• Do Problems – Page 17-18 (1-11)

• Not multiple choice!• Check odds in back of book

• Read and preload 1.3 information– Notes/vocab