Chapter 1: Scientific Thinking

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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?

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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.

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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?

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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