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Lab 1 Principles of Scientific Inquiry and the Scientific Method in the Anatomy and Physiology Lab

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    Learning Objectives.
    Completion of this lab exercise ensures that you will be able to…
            1.      Describe the difference between a scientific observation and a non-scientific observation
            2.      Outline the steps necessary to perform an experiment via the scientific method
            3.      Write a hypothesis to explain an observation that you made about how the human body functions.

    Pre-Lab Exercise:

    1. True/False: A hypothesis is the same as a guess as to what will happen in an experiment.                        
    2. All scientific experiment begins with either an                                                                                                  or a                                                 about a phenomenon.
    3. True/False: Being a scientist means following the scientific method of investigation to what is true and challenging your thoughts and assumptions about a topic through experimentation.
    4. Hypothesis should never:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   .
    5. One logical fallacy that you are aware of having made in the past is                                                                   .


    • Video


    Science and the Scientific Method

    Science is a process of learning and acquiring knowledge, and any person that does science is a “scientist.” This means that at any point in time we can all be scientists.  The only separation between students learning about human anatomy and physiology, and those in lab coats working to discover the cure for a disease is the approach to understanding a phenomenon.  The person performing as a “scientist” will work through a problem in a methodical approach that follows the logical rules of science.  The most important part of the rules of science is to not have a prejudiced view of what will happen.  Yes, you will have an idea based on previous experience, but you must approach every problem as a new experience.  When you approach each problem that you wish to solve as a new experience then you are beginning to use the scientific approach and thus are using science.
        There is no set way on how to do science beyond following the general rules of science. The rules of science, and the scientific method, are intended to make the process as objective as possible, and thereby gain some level of understanding that is as close to a “true reality” as possible.  One constant theme is that there is no certainty in science, only levels of probability and possibility for explaining the phenomenon being studied.   Because of this, scientific understanding can always be challenged, or even changed, with new observations, or different interpretations of previous observations. New tools and techniques have resulted in new observations, sometimes forcing revision of what had been taken as fact in the past.  With this ever-changing understanding and base of evidence there is only one certainty about science, which is, science does not “prove” it only allows for observations and explanations of those observations based on the assumptions that govern modern science.
        Underlying the world of modern science are four major assumptions that must be held as being true for observations to accurate, valid and reliable.  First of these assumptions is that the world is real, and that the physical universe exists and is not just our imagination.  This is regardless of whether, or not, it is something that can be sensed.  Secondly, humans (or animals) can accurately perceive the real world, and that humans can express such understanding.  Thirdly, processes that occur in nature can sufficiently explain the existence of the physical universe that we live in.  Lastly, that the process being observed operates the same way, everywhere and at all times within the physical universe.
        The way that we use these assumptions to study the human body and any other natural phenomenon is through the scientific method.  This method of learning follows a set of rules that leads to a process of asking and answering questions to search for cause-and-effect relationships in a phenomenon, or action, that we are examining.
        There are several rules of science that must be followed at all times.  First, all explanations must be based on careful observations that come through testing a hypothesis to explain a phenomenon.  Second, any hypothesis has a possibility and probability of being disproven (evidence from observation does not support the hypothesis).  Third, conclusions cannot be based simply on one’s opinion or belief (popular or otherwise) about the phenomenon.  Fourth, any observations and explanations must be based on the natural physical universe that can be sensed and perceived by everyone, in the same way at all times.  Fifth, that the best hypothesis is the choice for explaining the phenomenon that has the greatest amount of factual support, is based on logical analysis and makes the least number of assumptions to “best fit” all of the facts from the observations.  Lastly, science is not democratically fair! It is based on empirical evidence (observations) that stem from the logical flow of critical thought and analysis following the rules of science.
        It is very important to remember that the use of the scientific method is not developed to “prove” something “true”.  Instead, it is intended to test how, what, when, where, and why something occurred.  Because of this, we tend to think of the outcome of the use of the scientific method as leading to a contingent base of knowledge, rather than an absolute base of knowledge.  That understanding a phenomenon is based on what evidence can support our understanding at any given point in time.  This evidence changes over time and therefore our understanding of the phenomenon changes.
        How do we do this investigation?  The scientific method is a logical process that can be viewed as a sequential step-wise process that follows these key steps:

    1. Observation 
    2. Question about Observation: What? When? Where? Why? How? for the observation
    3. Hypothesis: explanation of the observation that answers the question based on deductive reasoning and understanding of the principles of science and previous knowledge
    4. Experimentation and Recording of Results: Reproducible step-wise sequence of events based on the phenomenon and scientific principles that tests the validity of the hypothesis where observed responses are recorded objectively
    5. Analysis of Results: logical statistical analysis of results used to accept or refute hypothesis 
    6. Interpretation and Inference of Analysis: logical process using inductive reasoning and inferential thinking to explain how analysis of results and observations made during the experimentation fits within understanding of the phenomenon and expands our overall knowledge of the principles and laws governing the phenomenon. Used to indicate the support for the hypothesis being tested
    7. Conclusion: terminal argument of inductive reasoning based on the principles of logical thought referred to as Occam’s Razor (the most logical explanation with the fewest number of assumptions is the most likely to be true) that terminates one cycle of the scientific method and can serve as the next hypothesis in a reproduced experiment


    How to Observe as a Scientist

    In order to be a good scientist and follow the scientific method of experimentation, we must be good at making observations. The means of observing is based on how we develop and execute our experiment. This is done through defining and controlling for factors that might impact the phenomenon that is being studied.  When designing an experiment, it is important that we are changing very little in the overall factors that can impact the phenomenon so that we can indicate that changes to one item causes something else to vary in a predictable way that allows us to draw a conclusion. The factors that are being observed and controlled are called variables.  
        There are two primary categories that all variables will fall into based on the amount of control that you have on the variable at any point of time of the experiment.  Those that you are able to change, or manipulate, are termed independent variables.  This variable can sometimes be referred to as the test condition.  While those that you have no control over, unable to change, are termed dependent variables.  The dependent variables are the variables that are being measured in any experiments. Along with these variables, there are other factors that have the ability to impact our observations. Those factors that we attempt to ensure don’t change or impact our experimental observations are referred to as control variables. In the studying of the human body, control variables typically fall under what is called “environmental conditions'' that is where we set up the test environment to have the participants of the study seen under the same condition (temperature, time of day, humidity, food).  There are also factors that we might try to control but have no control over yet will impact the dependent variable by acting as a different test condition. The variables that act as second independent variables are called confounding variables. When we do analysis and interpretation, we will take into consideration these confounding variables, as their influence will impact the assumptions that are made during the interpretation of the results.
        Underlying scientific observations are four major assumptions that must be held as being true for observations to be accurate, valid and reliable.  First of these assumptions is that the world is real, and that the physical universe exists and is not just our imagination.  This is regardless of whether, or not, it is something that can be sensed.  Secondly, humans (or animals) can accurately perceive the real world, and that humans can express such understanding.  Thirdly, processes that occur in nature can sufficiently explain the existence of the physical universe that we live in. Lastly, that the process being observed operates the same way, everywhere and at all times within the physical universe. The ability to ensure that your observations are valid and that the confounding variables are minimized makes for good experimental observations.  The ability to do this is through the constant recording of observations and journaling methods used to make the observations. The more thorough the notes you take during experimentation, the more controlled the experiment, the more likely your results are to be correct, and the more reproducible your experiment.


    How to write a hypothesis

    A hypothesis is your explanation of a phenomenon based on your understanding of the laws and principles of physiology. The statement is formed via a process known as deductive reasoning. A process that forces you to use what information you already know to explain why the observation that you are making has occurred.  It is not as many of you have learned previously a guess or a prediction. It is also not the explanation of observation based on the experimental outcome, that is the conclusion.  The conclusion can be seen as a possible hypothesis, but only for subsequent studies and experiments within the reproduction of the experimentation that is at the heart of scientific inquiry.  The hypothesis you have to view as your best explanation for why and how something occurs. 

        As such, it should be formulated and written in such a way so as to be supported or refuted by the evidence collected in the experiment. It is not a guess as to what might happen (that is a prediction) or an “if… then” statement (as this cannot be supported or refuted).  It is the explanation that you are going to test within the experiment. Being a good scientist means that your explanation will constantly undergo refinement and rewriting as new evidence and experimental analysis provides us with a greater understanding.

        What are the rules for writing the hypothesis?  When you write a hypothesis, there are a few key steps that need to be remembered for writing. First, there is never a “good” or a “bad” hypothesis, just one that is not well written. Second, there is never a “right” or a “wrong” hypothesis, just one that gets supported (shown to be possibly true) or refuted (shown to possibly be false). Third, a hypothesis is always written to be tested by evidence that can be seen and measured.


    Writing and Developing Hypothesis:

    • In order to develop the hypothesis, you need to develop the summary report (What am I studying? Why am I studying it? What am I going to do (what are the key steps I need to remember) in the experiment? What are my test conditions and measurements?
    • Be sure to focus on the purpose or the question that serves as the foundation for the experiment.  
    • The hypothesis needs to be written as a testable claim about the relationship between test condition (what you are doing) and measurements being collected (dependent variables). 
    • The hypothesis should never:
      • Use “if…then…” thinking
      • Form a tentative or conclusive claim
      • Be written to be too general (or specific) for the stated question that is being studied
      • Summarize the principle being studied
    • Hypothesis never is written as the statement of the law or principle being studied, or a restatement of the purpose.
    • Wording of the hypothesis must be open to interpretation that leads to it either being supported or refuted by the results of the experiment.


    Poor Example: Individuals will breathe more when exercising. (Statement that summarizes the tri-phasic response)

    Good Example: Females will have larger changes in tidal volumes than males of similar level of activity during and following a period of exercise.



    Clark, JE. 2010. Don’t Worry, It’s Only Science. TeachersPayTeachers.


    ACTIVITY 1: Scientific Method and Hypothesis Testing

    1. Watch the video that your instructor shows the class
    2. Based on what you see, make a hypothesis that would explain what you just watched.



    3. Share your hypothesis with your group and rewrite based on feedback provided



    4. Have your instructor check your hypothesis and within your group agree on 1 hypothesis to use for testing through experimentation.

    5. Develop the basic steps for your experiment.


    ACTIVITY 2: Discussion and Interpretation and Analysis of Results


    Discussions are written as well-organized paragraphs that allow you to discuss the meaning of your results from the experiment.  This is not a summary of what you did, that is the methods. The discussion involves using inductive reasoning and inferential thinking to formulate explain both what happened and why it happened.  This explanation involves using the principles to explain the observations and the observations to show how the principles hold to be true.  In performing your interpretation, you are linking your observed experimental results with the principles of human physiology.  This means you have to go back to what we already know about how the human body functions and then apply what do the results say about this understanding. You have to do this by limiting your assumptions and following a logical process of thinking. The logical process means that if you commit a fallacy in your thinking, then the entirety of your interpretation becomes nullified.  To make sure that you do not make these fallacies, be aware of these very common mistakes:

    • Hasty Generalization: This is a conclusion based on insufficient or biased evidence. In other words, you are rushing to a conclusion before you have all the relevant facts.
    • Post hoc ergo propter hoc/Because it happened last it must be the cause: This is a conclusion that assumes that if 'A' occurred after 'B' then 'B' must have caused 'A.' 
    • Begging the Claim: The conclusion provided is proven as being validated within the claim of the conclusion.
    • Petitio principii/Circular Argument: This restates the argument rather than actually proving it.
    • Either/or: This is a conclusion that oversimplifies the argument by reducing it to only two sides or choices.
    • Ad populum/Bandwagon Appeal: This is an appeal that presents what most people, or a group of people thinks, in order to persuade one to think the same way. 
    • Ignoratio elenchi/Red Herring: This diversionary tactic avoids the key issues, often by avoiding opposing arguments rather than addressing them.
    • Straw Man: This move oversimplifies an opponent's viewpoint and then attacks that hollow argument.
    • Argumentum ad ignorantiam/Appeal to ignorance: A conclusion that offers no proof of anything except that you don’t know something
    • False dilemma/False dichotomy: Conclusion that limits all options down to two supposed counter points and offers opinion that manipulates the argument into an either or statement
    • Slippery slope: Conclusion offers argument that outcome will likely lead to further outcomes that do not logically flow due to lack of evidence
    • Tu Quoque: conclusion does not provide argument but distracts from the argument due to a position that the opposite occurs from a hypocrisy in the opposing viewpoint
    • Ambiguity/Equivocation: Conclusion that confuses and misleads by stipulating that one thing is equal to something else
    • Non sequitur: a conclusion does not follow logically from what preceded it.
    • Argumentum ad verecundiam/Appeal to Authority: Conclusion that is justified because of citation of an experiment that agrees with the conclusion
    • Non causa pro causa/Causal Fallacy: any logical breakdown when identifying a cause based on argument revolving around unproven causal relationship

    When writing your discussion, think about the following (do not answer them as individual questions, instead use them to guide your thinking about the data and the analysis):  What does the results of the statistical analysis tell you about the relationship between observations? What does the correlations tell you about the relationship between the observations? (Think about: What is the importance of understanding the correlative values between measures (think about: What does the correlations tell me?  Does having a correlation between values mean anything about the change in one causing a change in the other?)? How does the relationship determined by your analysis align with the hypothesis (is it supported or refuted)?  What are limitations that could interfere with your ability to infer or induce a conclusion? (Think about: Where are the differences in the measures?  What does differences in measurements indicate?  What does the similarity between measures indicate? What errors might have occurred? How might errors in the experiment or analysis impact my results? How might accuracy impact the experimental conclusions that can be drawn?)


    1. Use the following set of data from an experiment that tested the hypothesis: Males will be larger and thus stronger than females.


    Number of Participants

    Average Days of Resistance Training/Weightlifting per week

    Average Height (cm)

    Average Body Mass (kg)

    Average BMI (kg/m2)

    Average Maximal Leg Press Load (kg)

    Ratio of Maximal Leg Press-to-Body Mass

    Whole Class








    Males Only








    Females Only








    2. Working as a group and based on what you are given, develop a discussion (based on your understanding of human anatomy and physiology) to explain the findings.


    Lab 1 Principles of Scientific Inquiry and the Scientific Method in the Anatomy and Physiology Lab is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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