3 Posing and Testing Methods Observation: The flashlight doesn’t work Question: What’s wrong with the flashlight Hypothesis: The batteries are dead Prediction: If the batteries are dead and you replace them with new ones, then the flashlight will work. Experiment: Replace the batteries.
4 Now you try: Observation : Question : Hypothesis : Prediction : Experiment :
5 What Makes A Good Biology Experi- ment?
6 1. Ask a testable Question. Example: Does watching T.V. make you fail Biology class?
7 2. Form a Hypothesis. Educated guess. Never in a question form.
8 3. Design a Controlled Experiment: A test where only one variable is being changed at one time.
9 What is involved in designing a good experiment? Set up a Control Group Set up a Experimental Group Determine which is the Independent Variable Determine which is the Dependent Variable Repeat the experiment to verify results Use a lot of sample groups in order to get the best indication of results Consider all Safety Issues Eliminate Experimental Error Prevent Bias AND REPEAT
10 3a. Control Group The group that does not receive the “treatment” (business as usual)
11 3b. Experimental Group The group that receives the “treatment” Only one variable is changed at a time.
12 3c. Independent Variable (manipulated variable) The variable that is deliberately changed in an experiment. (it is what I (the scientist) changes from one group to the other)
13 3d. Dependent Variable (or responding variable) The variable that changes because the independent variable changed. Depends on the Independent Variable
14 3e. Replication: How many times an experiment is done. 3f. Sample Size: The number of control & experimental groups.
15 3g. SAFETY!!! For the researcher For the Environment (Inside or outside labs) For the test subjects (like animals)
Two types of Error Operator Error –What the scientist did wrong Bias Falling Asleep during data collection Inaccurate measurements Equipment Error –What went wrong with equipment Dirty Glassware Equipment with incorrect increments for measurement 16
SET UP AN EXPERIMENT Shoe Brand’s Effect on Speed ** Add: “Dependent Variable: _____________” 17
18 Early Experiments in Transportation.
19 Farside Cartoon: G. Larson “Notice all the computations, theoretical scribblings, and lab equipment, Norm…Yes, curiosity killed these cats.”
20 3h. Identify sources experimental error. Bias: Preconceived ideas that influence experimenter. Operator or Equipment failure.
21 3i. How can you prevent bias?? bias Placebos- ½ test subjects given control or fake variable Blind-Study- test subjects don’t know if they have placebo or real Double-Blind- test subjects and scientists don’t know who has placebo or real
22 4. Collect Data. Think about how best to set up a data sheet. Will your data be qualitative or quantitative?
23 5. Analyze data. Create a graph, chart, or map to organize collected data.
24 6. Form conclusions. What patterns do you see?
25 7. Repeat Experiment. Do not change any variables!
27 What is involved in designing a good experiment? Set up a Control Group Set up a Experimental Group Determine which is the Independent Variable Determine which is the Dependent Variable Repeat the experiment to verify results Use a lot of sample groups in order to get the best indication of results Consider all Safety Issues Eliminate Experimental Error Prevent Bias AND REPEAT