LABORATORY EXERCISE # 1

THE SCIENTIFIC METHOD

 

 

LABORATORY  OBJECTIVES

 

Upon completion of this laboratory exercise the student will be able to:

 

1.  Identify the components of the scientific method and explain each.

 

2.  State a “good” hypothesis.

 

3.  Perform and evaluate a simple scientific experiment.

 

4.  Design a simple scientific experiment.

 

 

REFERENCE

 

Textbook:  chapter 1

 

 

INTRODUCTION

 

Science has been described as a way of knowing.  It emerges from man's curiosity about ourselves and the world around us.  Seeking to understand seems to be one of our basic drives.  We ask questions that arise from our observations of natural things; and we seek discovery of answers.  Striving to reveal the secrets of nature, scientists have devised a method of getting at the truth or solving problems.  This is called the scientific method.  Actually, there are many methods but they all bear common features or rules.

 

Is the scientific method something that only scientists can use?  Certainly not; its usefulness extends to all of us, even in our daily lives.  For example, I can use it to find why my car will not start.  Or, I can find out what foods give me a stomachache.

 

Despite what the scientist wants to find out and the exact procedure used, certain features of the scientific method are common. Scientists make observations that lead them to ask questions. They make educated guesses about possible answers, then devise ways to test their guesses. In its classical form the scientific method involves the following steps:

 

1.   Observation and Stating a Problem - Scientific investigations usually begin with an observation that stimulates a desire to know or understand.  The scientist then states the problem as clearly and concisely as possible.

 

2.   Collection of Pertinent Information - An attempt should be made to assemble the pertinent facts concerning the problem.  The scientist seeks to tap into as much available information about the problem as possible. This information may come from the library, the worldwide web, colleagues, or from other available sources.

 

 

3.   Formulation of a Hypothesis - Based on information assembled in step two above, a tentative explanation or hypothesis is advanced.  Some call this an educated guess.  This is a trial idea, a possible solution to the problem, and it is presented as a statement rather than a question.  A key feature of the hypothesis is that it can be tested or validated.

 

      What are some important characteristics of a “good” hypothesis?

 

 

 

 

4.   Testing the Hypothesis - In this step the scientist may design and execute an experiment to test the validity of the hypothesis.  The exact design of this test can vary greatly and depends on the nature of the study and the creativity of the investigator.  The experiment must be carefully planned and conducted with great precision. Scientists strive to eliminate all human and instrumental bias.  Accurate records as quantifiable data must be kept of every phase of the experiment.  Results of the experiment are gathered and analyzed.  Many experiments consist of a control group and an experimental group.  The experimental group is identical to the control group in every respect except one, called the variable.  The one substance, situation, etc. that is being tested is varied.  All other factors are kept constant in both the experimental group and the control group.  Therefore, the control serves as the basis or standard by which it is determined if the one variable is responsible for any differences in results.  A key feature of the experiment is that it must be repeatable.  That is, other researchers must be able to repeat the experiment under the same conditions and achieve the same results. 

 

      The controlled experiment is just one way of testing a hypothesis.  What are some other ways?

 

 

 

5.   Conclusion - When the experiment is complete, the researcher must evaluate the results in an

      effort to reach a conclusion.  The conclusion either supports or fails to support the original

      hypothesis.  In either case, knowledge is gained and the researcher moves on.

 

6.  Publication of Results - While your personal use of the scientific method does not involve

this step, it is vital to the scientist.  This requires publication, in appropriate scientific literature, of a detailed report of the problem, the hypothesis, all experimental methods and results, and the conclusions reached by the investigator.  This allows other scientists to repeat the investigation if they choose, as a way of confirming the validity of the study.

 

 

 

 

 

 

 

 

 

 

 

 

LABORATORY EXERCISE PROCEDURE

 

Use the indicated steps of the scientific method with each of the following three exercises.  These exercises are designed to provide some experience using the scientific method as a way to acquire knowledge. 

 

 Activity:

 

I.    The Tactics of Investigation:  The Black Box

 

One important objective in science is to devise explanations that have predictive value – explanations that can be applied to general classes of situations and that predict some results of some given sets of conditions.  Obviously, if predictive value is used as a criterion, not all explanations are equally good.  An explanation based on some omniscient or omnipotent demon is simple to devise but not especially predictive.  Unless the demon is constrained by some set of rules, one can’t really predict what he will do next.  And if one has the rules, then the demon, in a formal sense, is unnecessary.  The rules themselves are the explanation.  Unfortunately, concocting rules proves, as you will see, more difficult than devising demons.

 

Why should a scientific explanation be predictive?

 

 

In this exercise you will be presented with “black boxes.”  The original contents of each box (shoes, cigars, etc.) have been removed and replaced by some other object or material.  A display of materials or objects currently occupying the boxes will be provided by your instructor.  The problem is to predict what you would find if you were to open the box.  Observations can be made in any fashion – sound, smell, touch, weight – the only important limitation being that experiments must be non-destructive.  The measure of success is the precision with which the contents of the box are described.  Try to keep track of your different approaches to the problem so their relative usefulness can be judged after the box is opened.

 

Working in groups of four or five, spend no more than five minutes on a single box.  The instructor will arrange a competition among the groups.  (If you think science is always noncompetitive, guess again!)  In rotation each group will investigate all the provided boxes.  One person should act as a recorder and take down any conclusions that enjoy near-unanimity, along with the evidence and the arguments supporting them.  The recorder will probably spend most of his/her energy trying to get the team members to phrase their findings in some precise and succinct form, rather than accepting explanations involving “several thunkers and clankers.”  When the instructor observes that science has lurched forward sufficiently, the investigations will be halted.  At this point the recorder for each group will be asked to report briefly to the class on the findings of the group and the evidence supporting them.  Following each report, the boxes should be opened in the harsh glare of public gaze.

 

By this time you have undoubtedly noticed that certain approaches seem to be more useful than others.  Do preconceived ideas play any positive role, or are they always traps?  Ideas of how progress can be maximized have been formalized by previous investigators and philosophers of science,  using concepts such as hypotheses, crucial tests, predictions, confirming evidence, inferences, sampling, repeatability, degree of certainty, and so forth.  We will leave it to you to explore the applicability of these concepts of the “black box” exercise just completed.

 

Did some in your group seem consistently better at guessing than others?  Why do you suppose that is?

 

 

Which approaches seemed most useful?  Which yielded the poorest results?

 

 

 

Assuming you had unlimited access to laboratory equipment and techniques, what tests could you devise that would aid you in determining the contents of the black boxes?

 

 

 

 

II.  Conducting an Experiment:  The Step Test

 

      You have noticed that your heart rate seems to race when you physically exert yourself.  You wonder if the human heart rate increases as the intensity of exercise increases.  You can hypothesize that this is indeed the case.

 

A.  What do you observe?                                                                                                                        

 

 

B.  What problem or question has been identified?                                                                                

 

 

      C.  What is your hypothesis?                                                                                                                               

 

      D.  Experimentation:  We will work in groups of three or four students.  To obtain the necessary data, you must determine your heart rate at varying levels of physical exertion.  You will first monitor your heart rate at rest to establish a base line.  Lie down for at least five minutes, then determine your heart rate by monitoring your pulse rate.  (Blood surges through arteries each time your heart beats.)  Record your resting pulse rate in beats per minute.  The step exercise will be used at varying levels of intensity.  In this exercise you will step up one step, and then step back down.  Do this ten times in a one minute period. (Once every six seconds.)  Quickly monitor your pulse in beats per minute.  Record your pulse rate on the grid (graph) on page five.  Rest until your pulse rate nears your resting rate.  Repeat the step exercise and pulse reading for:  fifteen steps, twenty steps, twenty-five steps, thirty steps, thirty-five steps, and forty steps per minute. (If you are physically unable to perform the step exercise, substitute another mode of exertion which is measurable.  Or let another person do the step test.)  Summarize your results by plotting your heart rate against your exercise intensity on the graph below.  (Vertical axis is heart rate and horizontal axis is exercise intensity in steps per minute.)

 

 

 

 

 

 

     

            Interpret the graph in your own words.

 

           

           

            Is this a controlled experiment?

 

 

            Can you conclude:

           

                        That the heart rate is directly proportional to the intensity of physical exertion?

                        Why or why not?

 

 

That if we run this experiment on another student the results and conclusions will be the same?

Why or why not?

 

 

           

That the graph for a highly conditioned athlete would look similar to your graph?

Why or why not?

 

 

Could this test be repeated exactly by another researcher?

Why is repeatability of experimentation important?

 

 

Is this test valid/reliable?        

Why or why not?

 

 

Design/describe a better experiment that will yield results that are more reliable.

 

 

 

 

 

 

III.  Conducting an Experiment:  Extra-Sensory Perception -- ESP

 

      You have observed that you and your friend sometime have similar thoughts simultaneously.  You suspect that thoughts can be transmitted by "Extra Sensory Perception -ESP".

 

      A.  State the observation.                                                                                                                         

 

      B.  What problem or question has been identified?                                                                                 

 

      C.  The hypothesis is                                                                                                                                

 

      D.  Experimentation:  Sit back-to-back with a friend.  Choose and record a number between  one and five.  Concentrate and try to "send" the chosen number to your friend.  Give no  hints.  After a few seconds of concentration have your friend guess the number.  Record  the success or failure of the transmission.  Repeat the previous procedure fifty times. Summarize your results.

 

      E.  Conclusion                                                                                                                                         

 

      Answer all the follow-up questions for this experiment.

 

     

In how many of the trials did your selected number and that of your friend agree?                           

 

By sheer chance, how many of your trials should agree?                                                                   

 

Can you reach a valid conclusion?                                                  

      If yes, what is your conclusion?  If not, why not?

                                                                                                                                                                

 

If you and your friend were to agree on twenty of the fifty trials, does this prove that ESP is                a real phenomenon?                                                                                                                          

      Why or why not?

                                                                                                                                                                      

 

Can you note any bias in the experiment?       That is, is there anything about the test that

makes it more or less likely that you and your friend will agree?              

If yes, name some sources of bias. 

                                                                                                                                                                                                                                                                                           

 

Does this experimental design do what it is intended to do?

That is, is it valid?                Why or why not?                                                                                                                                                                                                                                                                                                      

 

 

Design another experiment which yields results that are more predictive and reliable than

this one.

 

 

 

 

 

 

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              

 

Can the validity of ESP really be proved or disproved?

      Explain.

 

 

IV.   Designing an Experiment

 

      The scientific method is nothing more than a logical and reliable method used to determine the truth or solve problems.  You can use it in your daily life to answer questions.  Suppose your father has always maintained that nitrogen fertilizer, properly applied, will consistently cause your grass to grow greener.  Design a simple, controlled experiment to determine whether   his assertion is true.