D O N OW A teacher had to select students to go on a field trip, but because they were all so wonderful, he decided to split the students into two groups of 10 (by last name.) He’s going to flip a coin, and heads will send A-L to the field trip, tails will send M-Z. Does every student have the same chance of going? Does every possible group of ten have the same chance of going?

O BJECTIVE 10.February.2011 Students will be able to… Use proper sampling techniques.

A GENDA Do Now (5 min) Hwork/Blinding (15 min) Sampling (15 min) Homework (5 min)

H WORK Due today: The Pepsi Challenge design.

B LINDING From Tuesday: Blind – when the test subjects don’t know if they are in treatment group or placebo group. Double Blind – personnel administering treatment don’t know if they are giving treatment or a placebo. Placebo – fake treatment in order to demonstrate level of control and compare results of treatment to results of no treatment.

S AMPLING Random Sampling – all members of a population are equally likely to be selected. Simple Random Sampling – any sample of n subjects is selected in such a way that every possible sample of the same size n has the same chance of being selected. Probability Sample – members of a population has a known but not necessarily the same probability of being selected.

R ANDOMNESS All Simple Random samples have to be Random. Not all Random samples have to be Simple Random.

O THER S AMPLING Systematic Sampling – selecting a starting point and then select every k th (such as every 50 th ) element of a population. Convenience Sampling – we use the results that are easiest to get. Stratified Sampling – we subdivide the population into at least two groups so that subjects in the same group share the same characteristics, and we take an equal number from each. Cluster Sampling – we first divide the population area into sections then randomly select some of those clusters, taking all the members from the selected clusters.

E XAMPLES At a police sobriety checkpoint, the cops were stopping every 5 th driver. An engineering student measures the strength of fingers used to push buttons by testing family members. A researcher for Spaulding athletic equipment is studying the relationship between the level of education and participation in any sport. She conducts a survey of 40 randomly selected golfers, 40 randomly selected tennis players, and 40 randomly selected swimmers.

H WORK Pg. 32, #17-30