Pre-Algebra Mrs. Spanier Sampling Pre-Algebra Mrs. Spanier

Questioning Should be fair No answer should appear better than another This is called bias

What is “Population”? The community (zip code, age, gender, etc…) of people whose opinions are sought. Usually so large and diverse that it is impossible to ask each member of the group every question. Why we select a sample.

Random Sample Members of the population are chosen in a way that all have an equal chance to be measured. Also called representative and proportionate sampling because all groups should be proportionately represented.

Stratified Sample Strata means to spread out. Population is divided into two or more strata (classes or groups) and each is sampled randomly.

Every nth member of the population is sampled. Systematic Sample Every nth member of the population is sampled.

What kind of sample? George went through the telephone book and called every 89th person listed. Systematic 5 students from each home room are questioned. Stratified

What kind of sample? Four people divided the telephone book evenly and each randomly sampled from their portion. Stratified

What kind of sample? A computer selects families all over the U.S. to receive a survey in the mail. Random

What kind of sample? Every 20th person to exit the Gap is questioned about their purchases. Systematic

The End

Happy Tuesday! 2 biased questions 1 fair question Tell your neighbor… About the 3 types of sampling methods 2 biased questions 1 fair question Day 2 of activity

Let’s Share… Find another pair from a different group. Discuss #1-6: Do your numbers agree? Are these answers valid? Why or why not?

Let’s Share… Discuss #7… Is each a valid sample? Too big, too small? World number is around 100 million and mostly women and children. Why do you think this is? Day 3 wrap up World Statistics