1. Identifying Independent and Dependent Variables
August 17, 2010
Biology I
Page 45 SATP Workbook

2. Important Terms to Know
Experiment-a set of steps that are performed to collect data.
Control group- stands as a standard for comparison
Experimental group- group that receives the treatment, drug, something ‘special’
Placebo-an inert (fake or inactive) substance that is usually given to the control group

3. Important Terms to Know
Independent Variable – what the experimenter uses or changes
Dependent Variable – what is measured in an experiment.

4. These are some questions that should be considered when setting up an experiment
What data should be collected and how?
How many groups will be used?
How many subjects/people per group should be used
What will be the control group?
Will there be a placebo used?
What are the important constants?.
What is the independent variable?
What is the dependent variable?

5. Tips on helping identify hypothesis, IV, DV, ect.
The hypothesis is usually presented in an “If-Then” statement. If not, it will show what someone ‘thinks’ will happen. Sometimes it is the first sentence in a paragraph.
In most written experiments, you can find the independent variable and the dependent variable in the first sentence.
In graph form, the independent variable is on the X-axis, and the dependent variable is on the Y-axis.

6. Example
Waldo wants to determine which fertilizer, X, Y, or Z, will cause corn plants to grown the fastest. He thinks that the corn plant that receives brand Y will grow the fastest because it contains the most phosphorous.
Identify the IV, DV, and the hypothesis.

7. Example pg 48
A pharmaceutical company gets FDA approval to test a memory enhancing drug on humans. The company chooses 100 participants and split them into two groups of 50 each. Once a day and over a period of 6 months, each participant is given a pill. In one group, the pill contains the medication. IN the other group, the pill contains no active ingredient. Once a week, the participants are given a test that measures their memory. The score for the test is recorded for each participant each week.