Do Now• Nine-year old Emily Rosa became an author of an article in the

Journal of the American Medical Association after she tested professional touch therapists. Using a cardboard partition, she held her hand above the therapist’s hand, and the therapist wwas asked to identify the hand that Emily chose. Is this an observation or an experiment?

Objectives• 8.February.2011• Students will be able to…• Design an experiment that is double blind.

Agenda• Do Now (5 min)• Hwork (5 min)• Experimental Design (15 min)• Short assignment (15 min)

Confounding• A researcher is doing an experiment to see which skin cream is

the most moisturizing. He has 10 patients, and he gives them three moisturizers. After three weeks, their skin is softer and more luxurious. What’s the conclusion of this experiment?

• Nothing, obviously, because he gave them all several things at once. Maybe one of them works, maybe they all work, maybe they only work together. This experiment sucks because he isn’t controlling his variables.

Blinding Experiments• In 1954, a massive experiment was designed to test the

effectiveness of the Salk vaccine. In the experiment, a treatment group was given the Salk vaccine, while a second group was given a placebo. This was a blind experiment.

• Treatment group – gets the actual treatment• Placebo/control group – gets a placebo/nothing.• Blind – the subjects don’t know which group they are in.

Why Blind?• The placebo effect, where people without getting the drug

report improvement (real or imagined.)

• Experiments can also be double blind, where even the people administrating the drug don’t know who is getting what. Only the person or people who designed the experiment are aware, and they don’t interact with the subjects.

Pepsi Challenge• How would we design this as a blind/double-blind

experiment?

Classwork• In groups:

• Design an experiment that is double blind.

Homework• Pg. 31 #6 to 12