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Scientific method


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Experimental Design Course

Experimental Design Course

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  • 1. EXPERIMENTAL DESIGN SCIENTIFIC METHOD Dr. Sanaa Abd Eltawab 1 & Dr. Rasha Aly Elsayed 2 1 Beni Suef University 2 Al Azhar University3rd Lecture
  • 2. Intended learning outcomes2  How Scientists Work: Solving the Problems  Definition of Scientific Method  Overview & Listing the Scientific Method Steps  Scientific Method Example - Observing - Questioning - Researching - Hypothesizing - Experimentation - Collect and record data - Analyzing data - Draw conclusions - Determine limitations - Publish results - Repeat Experiment
  • 3. How Scientists Work: Solving the Problems3  Much of biology deals with solving problems  These problems can be environmental, ecological, health related, etc.  No matter what types of problems are being studied, scientists use the same problem-solving steps called the Scientific Method  The scientific method, is the most powerful tool yet devised for the analysis and solution of problems in the natural world.
  • 4. Scientific Method: Definition4 Scientific method is a body of techniques for investigating phenomena and acquiring new knowledge, as well as for correcting and integrating previous knowledge. It is based on gathering observable, empirical and measurable evidence subject to specific principles of reasoning, the collection of data through observation and experimentation, and the formulation and testing of hypotheses.
  • 5. Scientific Method: Listing the Steps5  Make an Observation  Define the Problem  Research the Problem  State the Hypothesis  Experiment to test Hypothesis  Collect and Record Data  Analyze Data  Draw Conclusions  Determine Limitations  Report Results If needed, Do more investigation
  • 6. First What does the scientist want Question to learn more about? Then6 Research Gathering of information Next S O An “Educated” guess of an Hypothesis C answer to the question M V Then I E Written and carefully E Procedure/ followed step-by-step Method experiment designed to test the hypothesis E T R Next N H V Data Information collected during the experiment O I And And T Written description of what E Observations was noticed during the I D experiment W Finally F Conclusion Was the hypothesis correct or incorrect? I
  • 7. Scientific Method Ask Question7 Do Background Research Construct Think!Let’s break each Hypothesis Try Again of these steps Test with an down into their Experiment individual Analyze Results components: Draw Conclusion Hypothesis is False Hypothesis is True or Partially True Report Results
  • 8. Example for Scientific Method8 Example: the Scientific Method using Redi’s Experiment on Spontaneous Generation He was trying to disprove the idea of spontaneous Generation (or actually that flies came from maggots, which came from flies)
  • 9. 1. Observing9  Make an observation  See something unusual Redi wanted to show what caused the appearance of maggots (and then flies) on meat
  • 10. 2. Questioning10  Recognize, state or define the problem  Must be in the form of a question  The obvious question is:  What’s the source of these worms?
  • 11. Belief based on prior11 observations  Redi observed that maggots appeared on meat a few days after flies were on meat  No microscope = no way to see eggs  But Redi believed that maggots came from eggs that were laid by flies
  • 12. 12
  • 13. 3.13 Researching  Gather information related to the problem  Read, observe, measure, take samples, etc.
  • 14. 4. Hypothesizing14  A hypothesis is:  An educated guess, trial answer, possible solution, prediction  Must be a statement  Must be testable or measurable  Is based on your research and previous experience
  • 15. Forming a Hypothesis15Predict a possible answer to the problem or question. Redi’s Hypothesis: Flies produce maggots.  How could he test this?  Through a controlled experiment
  • 16. 5-Redi’s Controlled Experiment16  Redi used two groups of jars  Jars that contained meat and no cover  Jars that contained meat and gauze cover Jars with meat Uncovered jars Covered jars
  • 17. Control and Experimental Groups17  Control group: used as a standard of comparison  Experimental group: the group containing the factor (variable) that has been changed (manipulated or independent variable) Two groups of jars Uncovered jars Covered jars
  • 18. Variables in an Experiment18  Variables - Factors that can be changed VariablesControlled Variables Manipulated Variable – Responding Variable-- all the variables that (also called theremain constant Independent Variable) - (also called the factor in an experiment that Dependent Variable) - the a scientist purposely outcome or results, factor in changes an experiment that may change because of the manipulated variable what a scientist wants to observe
  • 19. Setting up a Controlled Experiment19  In a controlled experiment, only one factor is changed at a time.  Independent variable: the factor that is deliberately changed  Dependent variable: the factor that the scientist wants to observe; it changes in response to the independent variable
  • 20. Variables in Redi’s Experiment20  Controlled Variables: jars, type of meat, location, temperature, time  Manipulated Variables: gauze covering that keeps flies away from meat
  • 21. Let’s think about this.…21 Which is the control group? Uncovered jars Which is the experimental group? Covered jars Two groups of Jars with meat Uncovered jars Covered jars
  • 22. Redi’s Experiment on Spontaneous Generation OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat. HYPOTHESIS: Flies produce maggots.22 PROCEDURE Uncovered jars Covered jars Controlled Variables: jars, type of meat, location, temperature, time Several days pass Manipulated Variables: gauze covering that keeps flies away from meat Responding Variable: whether maggots appear Maggots appear No maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.
  • 23. 6. Collect and Record Data2320 Data: observations and measurements made in an experiment Types of Recorded Data  Quantitative - observations that involve measurements/numbers; i.e. 3 days, 12 maggots, 4 g, 13 sec, 8 liters  Qualitative - observations that do not involve numbers, are of a descriptive nature i.e. white maggots covered the meat, leaves were all wilting
  • 24. 7. Analyze the Data2421  Examine data tables, charts, and graphs  Examine experimental notes  Look for trends, patterns, and averages  What does the data show  Put your data into words
  • 25. 8. Draw Conclusions25  Restate the hypothesis: Example: Flies produce maggots.  Accept or reject the hypothesis.  Support your conclusion with specific, numerical data.  What was Redi’s conclusion?  Flies lay eggs too small to be seen.  Maggots found on rotting meat are produced from the eggs laid by flies.  Maggots are not appearing due to spontaneous generation!
  • 26. 9. Determine Limitations26  Scientists look for possible flaws in their research.  They look for faulty (inaccurate) data.  They look for experimental error or biass.  They decide on the validity of their results.  They make suggestions for improvement or raise new questions.
  • 27. 10. Publish Results27  Communication is an essential part of science  Scientists report their results in journals, on the internet, or at conferences  This allows their experiments to be evaluated and repeated  Scientists can build on previous Redi’s experiment on insects generation work of other scientists
  • 28. Repeating the Investigation28  Sometimes results are unexpected. Repeat the experiment!  John Needham challenged Redi’s experiment and designed his own to show that spontaneous generation CAN occur under certain circumstances.  Lazzaro Spallanzini designed a slightly different experiment to improve on Needham’s work
  • 29. Repeating the Experiment (continued)29  Louis Pasteur further modified the experiment.
  • 30. Thank You30