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NOTES Controlled Experiment: an experiment where all the factors/variables are kept the same except one (the independent variable). Variables: factors in an experiment that can be changed. Experimental Group: the one being tested. It gets the “drug” or treatment. Control Group: it is the exact duplication of the experimental group with the exception that it is lacking the one factor being tested. Instead of being "tested, " the control group is given a placebo (sugar pill) or some other inactive substance such as water. -This is known as the “Control”. Controlled Variables/Constants: factors that are kept the same in both the control and experimental groups.
NOTES-INDEPENDENT VS DEPENDENT VARIABLES Independent Variable: is controlled by the scientist in order to produce the data from the experiment that is needed to arrive at a conclusion. An experiment should have one independent variable. Dependent Variable: the variable that you measure as a result of the experiment. It is the data produced by the study.
EXAMPLES 1. How does taking diet pills effect weight loss? Independent Variable: Diet pill Dependent Variable: Weight Loss 2. How does studying effect test scores? Independent Variable: Studying Dependent Variable: Test scores 3. How does caffeine consumption affect heart rate? Independent Variable: Caffeine Dependent Variable: Heart rate
Controlled Experiment Example Question: Does light effect plant growth? (Plant growth can be indicated by measuring the size and/or number of leaves, surface area of leaves, height of plant or weight of plant). Hypothesis: If plants are given light, then they will grow. OR I think that plants that are given light will grow more. Experiment (Controlled)1. Experimental Group- 50 plants a. gets the treatment or independent variable which is “light” 2. Control Group- 50 plants a. does not get treatment- no light 3. Dependent Variable- plant growth 4. Controlled Variables/Constants: size, type, health of plant, water, humidity, temperature, growth container, soil type and amount of fertilizer or minerals.
ANALYSIS/CONCLUSION • After data is collected from both groups, the results of the experimental group is compared with the control group to determine the effect (or effectiveness) of whatever is being tested. • If the results from the control group and the experimental group are close, the experiment failed to produce a significant difference. • Based on the data produced in the experiment, the hypothesis will either be supported or not.
WAYS TO IMPROVE AN EXPERIMENT • Include a greater number of subjects (things being tested) • Include a greater number of trials involved in the experiment. - 500 - very significant; 100 - significant; 10 - not too significant; 1 - insignificant
Communicate your data • After completing an experiment that supports a scientists hypothesis, scientist submit their experimental data to PEER REVIEW Peer Review- other scientists check the method or repeat the experiment to repeat the results. This is important for a conclusion to be accepted as a THEORY. Theory: a body of knowledge that is accepted by most scientists. EX- Cell theory, Theory of Evolution etc.