Do Now 9/14

An ecologist is studying the relationship between rainfall and the number of forest fires in an area.

1. Write down a hypothesis that might explain the relationship.

2. Write down a prediction based on that hypothesis.

3. Write down the independent and dependent variables of the experiment.

Possible answers

• Hypothesis: several possibilities, including:– Decreased rainfall will increase the number of

fires, since dry areas are more easily burned.– Increased rainfall will decrease the number of

fires, because wet areas are less flammable– There is no connection between rainfall and fires,

since fires can happen in almost any environment– Etc. etc.

Possible Predictions

• REMEMBER: A prediction is an IF… THEN… statement based on a hypothesis– If the amount of rainfall decreases, then the

number of fires will increase.– If the amount of rainfall has no effect on the

number of fires, then the number of fires will not change in wet years or dry years.

Variables

• Independent Variable (IV): The thing that is thought to cause a change. (RAINFALL)

• Dependent Variable (DV): The thing that is thought to be affected by the IV. (FIRES)

Heading for a quiz!

• Friday• Topics:– Scientific Method, including• Hypotheses• Prediction• Independent & Dependent Variables• Controls

– Graphing and Measurement (tomorrow’s lesson)• 5 elements of a good graph• Where IV and DV go

– Bias (today’s lesson)

Control Groups

• The control group of an experiment is the samples that don’t get any of the experimental treatment.– Termite control group = Termites following black

BIC pen lines• The purpose of a control is to COMPARE it to

experimental samples. By comparing this way, differences between the control group and the experimental group must be due to the single tested independent variable.

Control Group Examples

• Testing the effectiveness of a fertilizer.• Testing the safety of a new drug.• Termite behavior…

• When can’t there be a good control?

Bias• What is bias?– Prejudice that favors some data or results over others.

• Only using data that supports or refutes a hypothesis, not all available data.

• Rigging an experiment to produce desired results.

• Why is it a bad thing?– Science must have accurate data to work properly.

• What causes bias– Confirmation bias: see what you want to see.– Conflicts of interest: $$$ and awards / promotions, etc.– Poor experimental design

Experiments

• Heart rate

• Telepathy / ESP

Pharmaceutical Company Bias

• Why Mr. Tomasino is a teacher, and not working for “the man.”

• Avandia article: ongoing lawsuits in the news

• Pfizer– Largest guilty plea ever (BILLION$$$)– Nigeria ethical issues

Assignments

• Complete the “find the bias” worksheet (front and back) for homework.