Title: Chapter 1: Scientific Thinking
1Chapter 1 Scientific Thinking
- Your best pathway to understanding the world
Lectures by Mark Manteuffel, St. Louis Community
College
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3Scientists
- 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?
4Science
- 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.
5How do you know that is true?
- The single question that underlies scientific
thinking
6- the importance of questioning the truth of many
scientific claims you see on merchandise
packages or read in the newspaper or on the
internet.
7- 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.
8Scientific 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
9Take-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.
101.2 Biological literacy is essential in the
modern world.
- A brief glance at any newspaper will reveal
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12Take-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.
131.3 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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15Understanding 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.
16The 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
17Scientific Thinking Is Empirical
- based on experience and observations that are
rational, testable, and repeatable.
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19What 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.
201.5 Step 1 Make observations.
- Look for interesting patterns or cause-and-effect
relationships.
21Does taking echinacea reduce the intensity or
duration of the common cold?
221.6 Step 2 Formulate a hypothesis.
- A proposed explanation for
- observed phenomena
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24To be most useful, a hypothesis must accomplish
two things
- It must clearly establish mutually exclusive
alternative explanations for a phenomenon. - It must generate testable predictions.
25The 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.
26Null 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.
271.7 Step 3 Devise a testable prediction.
- Suggest that under certain conditions we will
make certain observations.
28Devising a Testable Prediction from a Hypothesis
- Keep in mind any one of several possible
explanations could be true. -
29Devising 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.
30Hypothesis Echinacea reduces the duration and
severity of the symptoms of the common cold.
311.8 Step 4 Conduct a critical experiment.
- an experiment that makes it possible to
decisively determine whether a particular
hypothesis is correct
32Hypothesis Echinacea reduces the duration and
severity of the symptoms of the common cold.
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36Take-home message 1.8
- A critical experiment is one that makes it
possible to decisively determine whether a
particular hypothesis is correct.
371.9 Step 5 Draw conclusions, make revisions.
38The 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.
39Making Revisions
- Try to further refine a hypothesis.
- Make new and more specific testable predictions.
40Does echinacea help prevent the common cold?
Hypothesis Echinacea reduces the duration and
severity of the symptoms of the common cold.
411.10 When do hypotheses become theories?
- Two distinct levels of understanding that
scientists use in describing our knowledge about
natural phenomena
42Hypotheses and Theories
- A hypothesis is a proposed explanation for a
phenomenon. - a good hypothesis leads to testable predictions.
43Hypotheses 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
44Theories vs. Hypotheses
- Repeatedly tested
- Broader in scope
45Take-home message 1.10
- Scientific theories do not represent speculation
or guesses about the natural world.
46Take-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.
47- 1.11 Controlling variables makes experiments
more powerful.
48Elements 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
49Controlling 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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51Is arthroscopic surgery for arthritis beneficial
for the 300,000 people who have it each year?
52The 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.
53Clever Hans
54Experimental 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.
55Hallmarks of an Extremely Well-designed
Experiment
- Blind/double-blind strategies
- Randomized
- The subjects are randomly assigned into
experimental and control groups.
561.12 Repeatable experiments increase our
confidence.
- Can science be misleading?
- How can we know?
571.13 Weve got to watch out for biases.
- Can scientists be sexist?
- How would we know?
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59Take-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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61- 1.14 Statistics can help us to make decisions.
62Statistics
- A set of analytical and mathematical tools
designed to help researchers gain understanding
from the data they gather.
63- Larger numbers of participants are better than
fewer if you want to draw general conclusions
about natural phenomena.
64Making 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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66Statistics 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
67- Correlation is not causation.
- Statistical analyses can help us to organize and
summarize.
68Take-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.
691.15 Pseudoscience and misleading anecdotal
evidence can obscure the truth.
70- 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.
71Four 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.
72Anecdotal Observations
- do not include a sufficiently large and
representative set of observations of the world - data are more reliable than anecdotes
73Take-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.
741.16 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?
75One 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