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Overview of the scientific method

Overview of the scientific method

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  • 1. Copyright © 2009 Pearson Education, Inc. © 2013 Pearson Education, Inc. PowerPoint Lecture prepared by Jill Feinstein Richland Community College Fourth Edition BIOLOGYScience for Life | with Physiology Colleen Belk • Virginia Borden Maier ChapterChapter 11 Can Science Cure the Common Cold? Introduction to the Scientific Method * Components of this PowerPoint were altered by Lissa Walls to better fit the learning objectives of Integrated Science: The Living World (SCI 106) *
  • 2. © 2013 Pearson Education, Inc. 1.1 The Process of Science  Science refers to a body of knowledge  Science is not a giant collection of facts to be memorized.  It is important to learn about the process of science called the scientific method.  The scientific method is used to solve problems and answer questions.  Observations  Proposing ideas  Testing ideas  Discarding or modifying ideas based on results
  • 3. © 2013 Pearson Education, Inc. 1.1 The Process of Science The Nature of Hypotheses  Hypothesis: proposed explanation for a set of observations  Scientific Hypotheses need to be:  Testable –possible to examine the hypothesis through observations  Falsifiable –able to be proven false if it is untrue  Objective – not influenced by personal feelings or opinions  Ethical - moral
  • 4. © 2013 Pearson Education, Inc. 1.1 The Process of Science Where do hypotheses come from?  Both logical and creative influences are used to develop a hypothesis
  • 5. © 2013 Pearson Education, Inc. 1.1 The Process of Science Scientific Theory  Powerful, broad explanation of a large set of observations  Based on well supported hypotheses  Supported by research from several different independent sources
  • 6. © 2013 Pearson Education, Inc. 1.1 The Process of Science Steps of the Scientific Method  The process looks something like this:
  • 7. © 2013 Pearson Education, Inc. 1.1 The Process of Science
  • 8. © 2013 Pearson Education, Inc. 1.1 The Process of Science The Logic of Hypothesis Tests  A hypothesis that fails our test is rejected and considered disproven.  A hypothesis that passes is supported, but not proven.  Why not? An alternative hypothesis might be the real explanation.
  • 9. © 2013 Pearson Education, Inc. 1.2 Hypothesis Testing The Experimental Method  Experiments are designed to test specific hypotheses.  Variables: factors that can change in value under different conditions  Independent variables can be manipulated by the scientist  Dependent variables cannot be changed by the researcher  Standardized variables (aka controlled variables) kept constant so that any difference in outcome is due ONLY to treatment
  • 10. © 2013 Pearson Education, Inc. 1.2 Hypothesis Testing Controlled Experiments  Controlled experiment: tests the effect of a single variable  Control: a subject (or group) who is not exposed to the experimental treatment but has all other variables the same  Given either no treatment or a placebo
  • 11. © 2013 Pearson Education, Inc. 1.2 Hypothesis Testing Controlled Experiments  Differences seen between the experimental group and control group can be attributed to the experimental treatment  Random Assignment  An effective way of assigning individuals to groups for testing
  • 12. © 2013 Pearson Education, Inc. 1.2 Hypothesis Testing Controlled Experiments  Example: Echinacea tea experiment:  Hypothesis: drinking Echinacea tea relieves cold symptoms  Experimental group drinks Echinacea tea 5-6 times daily  Control group drinks “sham” Echinacea tea 5-6 times daily (placebo)  Both groups rated the effectiveness of their treatment on relieving cold symptoms
  • 13. © 2013 Pearson Education, Inc. 1.2 Hypothesis Testing Controlled Experiments  People who received echinacea tea felt that it was 33% more effective at reducing symptoms
  • 14. © 2013 Pearson Education, Inc. 1.2 Hypothesis Testing Minimizing Bias in Experimental Design  If human subjects know whether they have received the real treatment or a placebo, they may be biased.  Blind experiment: subjects do not know what kind of treatment they have received  Double blind experiment: the person administering the treatments and the subjects do not know who is in each group until after the experiment is over
  • 15. © 2013 Pearson Education, Inc. 1.2 Hypothesis Testing Minimizing Bias in Experimental Design
  • 16. © 2013 Pearson Education, Inc. 1.2 Hypothesis Testing  The “gold standard” for experimentation  Double-blind, placebo controlled, and randomized experiments  Model systems can be used in experiments when it appears too dangerous or unethical to test on humans  examples: mice, rats, dogs and pigs  A correlation can be used to test hypotheses when controlled experiments on humans are impossible to perform
  • 17. © 2013 Pearson Education, Inc. 1.2 Hypothesis Testing Using Correlation to Test Hypotheses  Using existing data, is there a correlation between variables?  Hypothesis: stress makes people more susceptible to catching a cold  Is there a correlation between stress and the number of colds people have caught?
  • 18. © 2013 Pearson Education, Inc. 1.2 Hypothesis Testing Using Correlation to Test Hypotheses  Results of such a study: the number of colds increases as stress levels increase  Caution! Correlation does not imply causation!!
  • 19. © 2013 Pearson Education, Inc. 1.2 Hypothesis Testing Using Correlation to Test Hypotheses  The correlation might be due to other reasons
  • 20. © 2013 Pearson Education, Inc. 1.3 Understanding Statistics Overview: What Statistical Tests Can Tell Us  Data collected during experimentation should be organized and analyzed using statistical methods  Comparing means (averages) is a common way to compare the data from two groups  Statistical tests will tell us if differences between groups are due to treatment or due to chance  Statistically significant: unlikely the observed difference is due to chance IF experiment was designed and carried out properly  AKA there is a true difference between the two groups/items compared
  • 21. © 2013 Pearson Education, Inc. 1.3 Understanding Statistics The Problem of Error  During experimentation researchers need to minimize error; errors affect the outcome of experiments  Experimental error: inconsistent or incorrect measurements, poorly functioning equipment, timing errors, confusing instructions to subjects, etc.  Sampling error: estimation error because of surveying a sample of the population rather than the whole population  Sample size: the number of units (people, plants, animals, illnesses) to be tested/surveyed in an experiment  A larger sample size is more true of the population from which the sample was taken
  • 22. © 2013 Pearson Education, Inc. 1.3 Understanding Statistics What Statistical Tests Cannot Tell Us  If an experiment was designed and carried out properly  If observer error occurred; statistical tests can only evaluate the probability of sampling error  Practical or biological significance of results
  • 23. © 2013 Pearson Education, Inc. 1.4 Evaluating Scientific Information Primary Sources  Researchers can submit a paper about their experimental methods and results to a professional journal (primary source)  Primary Sources undergo peer review: evaluation of submitted papers by other experts  Secondary sources: books, news reports, the internet, and advertisements
  • 24. © 2013 Pearson Education, Inc. 1.4 Evaluating Scientific Information Information from Anecdotes  Anecdotal evidence is based on one person’s experience, not on experimental data  Example: a testimonial from a celebrity
  • 25. © 2013 Pearson Education, Inc. 1.4 Evaluating Scientific Information Science in the News
  • 26. © 2013 Pearson Education, Inc. 1.4 Evaluating Scientific Information Science in the News  Secondary sources may be missing critical information or report the information incorrectly  Consider the source of media reports  Be careful with the Internet since anyone can post information  Be very cautious about claims made in paid advertisements
  • 27. © 2013 Pearson Education, Inc. 1.4 Evaluating Scientific Information Understanding Science from Secondary Sources  Use your understanding of the scientific method to evaluate findings stated by secondary sources  News media generally highlight only those science stories that seem newsworthy  They are more likely to report a positive result than a negative one
  • 28. © 2013 Pearson Education, Inc. 1.5 Is There a Cure for the Common Cold?  No, but prevention methods are known  Wash your hands!  No effect on cold susceptibility:  Vitamin C  Exposure to cold temperatures  Exercise  No vaccine for the common cold