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Life Science 15: Concepts and IssuesLecture 3: Scientific thinking and decision making1/17/12I. Scientific thinking- an efficient way to learn about and understand the worldII. Hypotheses must be tested with critical experimentsIII. Controlling variables makes an experiment powerfulIV. Avoid the lure of pseudoscience and anecdotal observationsScientific Method:1. observations2. hypothesis3. predictions4. experiments5. conclusions, revise hypothesisQ: Does it rain more on weekends?-take data on spreadsheet-rains 22% more on Saturdays than Mondays- WHY?- idea-more particulate matter on weekends due to build-up all week from more driving,enhances cloud formation and therefore rain-where did they measure the rainfall? East coast-in the ocean, it rains everyday equally Scientific thinking illuminates situations in which we should change what we think.The “Critical Experiment”-putting a hypothesis to the test-the results can decisively determine whether a hypothesis is correctQ: Is maze running ability in mice genetic?-test how many errors mice make in a maze over multiple times-observation: variance in ability appears hereditary-hypothesis: maze running ability is genetically influenced-test: each generation, test all mice for maze-learning ability, then breed the top 20% and the bottom 20%At the core of scientific thinking is the ability to imagine a critical experiment.How can you increase your experiment’s power?1. Randomize: subjects across control and experimental groups (ex. Paternitystudy)2. Control your study: if we want to attribute a difference between two groups to the experimental treatment, there must be no underlying differences between the groups. (ex. Sleep study)3. Use a double-blind design (ex. Symmetry study)Beware of Pseudoscience:Scientific thinking is powerful but can be costly, time-consuming, and difficultCheating has an appeal“9/10 doctors recommend brand X”-how many were asked?-how were they selected?-alternative?Beware of Anecdotes:We are overly biased by observations not based on careful study and/or not representative of the norm.Autism is diagnosed right around the time children are vaccinated for measles, mumps, and rubella.-what conclusion is tempting?Pseudoscience and anecdotal observations can be almost unbearable appealing, but shouldn’t influence our


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UCLA LIFESCI 15 - Scientific thinking

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