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Title: Chapter 1: Scientific Thinking


1
Chapter 1 Scientific Thinking
  • Your best pathway to understanding the world

Lectures by Mark Manteuffel, St. Louis Community
College
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Scientists
  • Are curious
  • Ask questions about how the world works
  • Seek answers
  • Does the radiation released by cell phones cause
    brain tumors?
  • Are anti-bacterial hand soaps better than regular
    soap?
  • Do large doses of vitamin C reduce the likelihood
    of getting a cold?

4
Science
  • Not simply a body of knowledge or a list of facts
    to be remembered
  • but rather an intellectual activity,
    encompassing observation, description,
    experimentation, and explanation of natural
    phenomena.

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How do you know that is true?
  • The single question that underlies scientific
    thinking

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  • the importance of questioning the truth of many
    scientific claims you see on merchandise
    packages or read in the newspaper or on the
    internet.

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  • You dont have to be at the mercy of cranks,
    charlatans, advertising, or slick packaging.
  • Learn exactly what it means to have scientific
    proof or evidence.
  • Learn what it means to think scientifically.

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Scientific Literacy
  • how to think scientifically
  • how to use the knowledge we gain to make wise
    decisions
  • increasingly important in our lives
  • literacy in matters of biology is especially
    essential

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Take-home message 1.1
  • Through its emphasis on objective observation,
    description, and experimentation, science is a
    pathway by which we can come to discover and
    better understand the world around us.

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1.2 Biological literacy is essential in the
modern world.
  • A brief glance at any newspaper will reveal

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Take-home message 1.2
  • Biological issues permeate all aspects of our
    lives.
  • To make wise decisions, it is essential for
    individuals and societies to attain biological
    literacy.

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1.3 The scientific method is a powerful approach
to understanding the world.
  • If science proves some belief of Buddhism wrong,
    then Buddhism will have to change
  • Dalai Lama, 2005

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Understanding How the World Works
  • Someone wonders about why something is the way it
    is and then decides to try to find out the
    answer.
  • This process of examination and discovery is
    called the scientific method.

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The Scientific Method
  • Observe a phenomenon
  • Propose an explanation for it
  • Test the proposed explanation through a series of
    experiments
  • ?
  • Accurate valid,
  • or
  • Revised or alternative explanations proposed

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Scientific Thinking Is Empirical
  • based on experience and observations that are
    rational, testable, and repeatable.

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What should you do when something you believe in
turns out to be wrong?
  • This may be the most important feature of the
    scientific method
  • it tells us when we should change our minds.

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1.5 Step 1 Make observations.
  • Look for interesting patterns or cause-and-effect
    relationships.

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Does taking echinacea reduce the intensity or
duration of the common cold?
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1.6 Step 2 Formulate a hypothesis.
  • A proposed explanation for
  • observed phenomena

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To be most useful, a hypothesis must accomplish
two things
  1. It must clearly establish mutually exclusive
    alternative explanations for a phenomenon.
  2. It must generate testable predictions.

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The Null Hypothesis
  • A negative statement that proposes that there is
    no relationship between two factors
  • These hypotheses are equally valid but are easier
    to disprove.
  • An alternative hypothesis
  • It is impossible to prove a hypothesis is
    absolutely and permanently true.

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Null and Alternative Hypotheses
  • Echinacea reduces the duration and severity of
    the symptoms of the common cold.
  • Or as a null hypothesis
  • Echinacea has no effect on the duration or
    severity of the symptoms of the common cold.

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1.7 Step 3 Devise a testable prediction.
  • Suggest that under certain conditions we will
    make certain observations.

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Devising a Testable Prediction from a Hypothesis
  • Keep in mind any one of several possible
    explanations could be true.

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Devising a Testable Prediction from a Hypothesis
  • The goal is to
  • Propose a situation that will give a particular
    outcome if your hypothesis is true
  • but that will give a different outcome if your
    hypothesis is not true.

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Hypothesis Echinacea reduces the duration and
severity of the symptoms of the common cold.
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1.8 Step 4 Conduct a critical experiment.
  • an experiment that makes it possible to
    decisively determine whether a particular
    hypothesis is correct

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Hypothesis Echinacea reduces the duration and
severity of the symptoms of the common cold.
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Take-home message 1.8
  • A critical experiment is one that makes it
    possible to decisively determine whether a
    particular hypothesis is correct.

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1.9 Step 5 Draw conclusions, make revisions.
  • Trial and error

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The Role of Experiments
  • What is important is that we attempt to
    demonstrate that our initial hypothesis is not
    supported by the data.
  • If it is not, we might then adjust our
    hypothesis.

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Making Revisions
  • Try to further refine a hypothesis.
  • Make new and more specific testable predictions.

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Does echinacea help prevent the common cold?
Hypothesis Echinacea reduces the duration and
severity of the symptoms of the common cold.
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1.10 When do hypotheses become theories?
  • Two distinct levels of understanding that
    scientists use in describing our knowledge about
    natural phenomena

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Hypotheses and Theories
  • A hypothesis is a proposed explanation for a
    phenomenon.
  • a good hypothesis leads to testable predictions.

43
Hypotheses and Theories
  • A theory is a hypothesis for natural phenomena
    that is exceptionally well-supported by the data.
  • a hypothesis that has withstood the test of time
    and is unlikely to be altered by any new evidence

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Theories vs. Hypotheses
  • Repeatedly tested
  • Broader in scope

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Take-home message 1.10
  • Scientific theories do not represent speculation
    or guesses about the natural world.

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Take-home message 1.10
  • Theories are hypotheses that have been so
    strongly supported by empirical observation that
    the scientific community views them as very
    unlikely to be altered by new evidence.

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  • 1.11 Controlling variables makes experiments
    more powerful.

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Elements Common to Most Experiments
  • 1. Treatment
  • any experimental condition applied to individuals
  • 2. Experimental group
  • a group of individuals who are exposed to a
    particular treatment
  • 3. Control group
  • a group of individuals who are treated
    identically to the experimental group with the
    one exception they are not exposed to the
    treatment
  • 4. Variables
  • characteristics of your experimental system that
    are subject to change

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Controlling Variables
  • the most important feature of a good experiment
  • the attempt to minimize any differences between a
    control group and an experimental group other
    than the treatment itself

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Is arthroscopic surgery for arthritis beneficial
for the 300,000 people who have it each year?
  • How do we know?

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The Placebo Effect
  • The phenomenon in which people respond favorably
    to any treatment
  • The placebo effect highlights the need for
    comparison of treatment effects with an
    appropriate control group.

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Clever Hans
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Experimental Designs
  • Blind experimental design
  • The experimental subjects do not know which
    treatment (if any) they are receiving.
  • Double-blind experimental design
  • Neither the experimental subjects nor the
    experimenter knows which treatment the subject is
    receiving.

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Hallmarks of an Extremely Well-designed
Experiment
  • Blind/double-blind strategies
  • Randomized
  • The subjects are randomly assigned into
    experimental and control groups.

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1.12 Repeatable experiments increase our
confidence.
  • Can science be misleading?
  • How can we know?

57
1.13 Weve got to watch out for biases.
  • Can scientists be sexist?
  • How would we know?

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Take-home message 1.13
  • Biases can influence our behavior, including our
    collection and interpretation of data.
  • With careful controls, it is possible to minimize
    such biases.

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  • 1.14 Statistics can help us to make decisions.

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Statistics
  • A set of analytical and mathematical tools
    designed to help researchers gain understanding
    from the data they gather.

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  • Larger numbers of participants are better than
    fewer if you want to draw general conclusions
    about natural phenomena.

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Making Wise Decisions About Concrete Things
  • Does having access to a textbook help a student
    to perform better in a biology class?
  • Students who had access to a textbook scored an
    average of 81 8 on their exams
  • while those who did not scored an average of 76
    7.

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Statistics can also help us to identify
relationships (or the lack of relationships)
between variables.
  • a positive correlation
  • meaning that when one variable increases, so does
    the other

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  • Correlation is not causation.
  • Statistical analyses can help us to organize and
    summarize.

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Take-home message 1.14
  • Because much variation exists in the world,
    statistics can help us evaluate whether
    differences between a treatment and control group
    can be attributed to the treatment rather than
    random chance.

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1.15 Pseudoscience and misleading anecdotal
evidence can obscure the truth.
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  • Pseudoscience individuals make
    scientific-sounding claims that are not supported
    by trustworthy, methodical scientific studies.
  • Anecdotal observations based on only one or a
    few observations, people conclude that there is
    or is not a link between two things.

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Four out of five dentists surveyed recommend
sugarless gum for their patients who chew gum.
  • How do they know what they know?
  • Maybe the statement is factually true, but the
    general relationship it implies may not be.

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Anecdotal Observations
  • do not include a sufficiently large and
    representative set of observations of the world
  • data are more reliable than anecdotes

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Take-home message 1.15
  • Pseudoscience and anecdotal observations often
    lead people to believe that links between two
    phenomena exist, when in fact there are no such
    links.

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1.16 There are limits to what science can do.
  • The scientific method will never prove or
    disprove the existence of God.
  • Understand elegance?
  • What is beauty?

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One of Several Approaches to the Acquisition of
Knowledge
  • The scientific method is, above all, empirical.
  • Value judgments and subjective information
  • Moral statements and ethical problems
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