scientific methodpowerpoint
DESCRIPTION
Overview of the scientific methodTRANSCRIPT
Copyright © 2009 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
PowerPoint Lecture prepared byJill Feinstein
Richland Community College
Fourth Edition
BIOLOGYScience for Life | with Physiology
Colleen Belk • Virginia Borden Maier
ChapterChapter 1 1
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)
*
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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
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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
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1.1 The Process of Science
Where do hypotheses come from?
Both logical and creative influences are used to develop a hypothesis
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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
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1.1 The Process of Science
Steps of the Scientific Method
The process looks something like this:
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1.1 The Process of Science
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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.
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1.2 Hypothesis TestingThe 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
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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
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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
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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
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1.2 Hypothesis Testing
Controlled Experiments
People who received echinacea tea felt that it was 33% more effective at reducing symptoms
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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
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1.2 Hypothesis Testing
Minimizing Bias in Experimental Design
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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
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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?
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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!!
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1.2 Hypothesis Testing
Using Correlation to Test Hypotheses
The correlation might be due to other reasons
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1.3 Understanding StatisticsOverview: 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
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1.3 Understanding StatisticsThe 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
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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
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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
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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
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1.4 Evaluating Scientific Information
Science in the News
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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
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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
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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