Thinking Like a Scientist Science starts with an observation Observation – the process of gathering information in a careful, orderly way  Use your senses: Sight Hearing Touch Smell Taste

Data – information gathered from observation Two Types:  Quantitative = numbers There are 7 birds at the feeder  Qualitative = descriptive using characteristics that can't be counted The bird has a red head. Inference - a logical interpretation based on prior knowledge and experience

Setting up a Controlled Experiment  Controlled experiment - tests the effect of a one variable  Variables -factors in an experiment

 Independent variable – a factor that is changed by the scientist  Dependent variable – the factor that is observed/ measured may change in response to the independent variable.

Control Group The control group is exposed to the same conditions as the experimental group, except for the variable being tested. In a scientific experiment, the control is the group that serves as the standard of comparison. All experiments should have a control group!

Constants The constants in an experiment are all the factors that the experimenter attempts to keep the same. All other factors are kept the same so that any observed changes in the experiment can be attributed to the variable.

Example: In order to test the effectiveness of a new vaccine, 50 volunteers are selected and divided into two groups. One group will be the control group and the other will be the experimental group. Both groups are given a pill to take that is identical in size, shape, color and texture. Describe the control group. Describe the experimental group. What variables are kept constant? What is the independent variable? Even though the volunteers are given identical looking pills, the control group will not actually receive the vaccine. This group will receive the vaccine. The size, shape, color, and texture of the pill. Whether or not the pill contains the vaccine.

When Experiments Are Not Possible Ethical considerations prevent certain experiments  Ex) determine the effects on people of a chemical suspected of causing cancer In field studies, such as animals in the wild, researchers try not to disturb natural systems when observing Scientists choose volunteers who may already be exposed and compare them to a group who has not