The Scientific Method (Experimental Design) A plan used to collect, organize and explain information (answers a question about an observation that was made) Based on: 1. Observations: 2. Inferences: data gathered with our 5 senses & scientific instruments interpretation of observations (conclusions)
The Scientific Method Make an observation Ask a question (Problem) Ask a question (Testable prediction) Develop a hypothesis Test hypothesis with a controlled experiment Revise hypothesis and re-test Repeat experiment multiple times to obtain consistent results. Collect and analyze data and make conclusions Hypothesis is supported Hypothesis is not supported Potentially develops into a theory
C. Design a controlled experiment to test the hypothesis. 1. Only one variable is manipulated by the experimenter. (Everything else must be the same – constants) a. The independent variable (manipulated variable) is the Ex. The type of plant food given to each of 4 pea plants. *Constants: one that the experimenter alters and that will cause change in another variable. same amount of light, water, temperature etc. Food A Food B Food C Food D
b. The dependent variable (responding variable) is Height of each of the 4 pea plants after a specific period of time. the one that changes in response to the independent variable (the results). Ex. D A C B
2. test groups… Two b. Control group: a. Experimental Group: use a LARGE sample size (lots of test subjects b. Control group: exposed to “normal” conditions for comparison (lacks the independent variable) Ex. A 5th pea plant that does not receive any plant food…... only light, water etc. a. Experimental Group: the independent variable is present/changed in this group Food A Food B Food D Food C
*Control group may be given a placebo – substance containing no medicine, such as a sugar pill *In the conclusion, compare experimental group results to control group results
D. To Make an Experiment More Valid: 2. Use a larger sample size (more specimens) Repeat the experiment