The Scientific Method and Experimental Design A. Scientific Method” a comprehensive (non-linear), logical problem solving process a. Steps of the scientific method i. Observation (qualitative and quantitative): done throughout the scientific process. ii. Identify the problem or question iii. Hypothesis(es): Educated guess as to the solution of the problem. Must show cause and effect (e.g., “If…Then…Because…). Must include both independent and dependent variables. iv. Prediction: Expected results (typically quantitative: graph) v. Experimentation 1. Includes materials and methods 2. Types of: Lab experiments or controlled experiments, field experiments or natural experiments, hybrid experiments (field + lab), models that predict reality (e.g., climate models that predict long-term forecasts using many variables) a. Blind Studies i. Single-blind: subjects receiving the treatment (experimental group) don’t know they are receiving it. ii. Double-blind: neither the treatment group nor the researcher knows who is receiving the treatment. The researcher only finds out who received it after the study is over. vi. Results (data): Usually in tables vii. Analysis: What you DO to the data 1. examples: graphs, %, averages viii. Conclusions: revisit hypothesis (es): Hypothesis supported by data or not? Hypotheses are NOT right or wrong as conclusions are as only as good as your data (i.e., experimental error) ix. Theory: Hypothesis widely supported by multiple experiments from different researchers. Theories can be wrong (e.g., technology changes) x. Law: Fact! The theory fails to be proven faulty. B. Experimental Design a. All good experiments must have i. 1 or more hypotheses (see above) and predictions (i.e., expected results) ii. control group iii. treatment group (manipulate independent variables) iv. Identify control or confounding variables v. Replication (independent, repeated trials of the experiment) vi. A large sample size that is randomly selected (no bias) using a random number generator or table, or randomly drawing from a hat like a lottery. vii. Measurements of the dependent variable (what are you observing? It must be measurable!!!) viii. Mathematical or statistical comparison between experimental (treatment) and control groups ix. Description of results: Graph (labeled) and/or a data table that is consistent with the experimental design.
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