Laboratory 1: The Scientific Method
Laboratory 1: The Scientific Method
Objectives: After completing this laboratory exercise, you should be able to:
⦁ Describe the steps involved in the scientific method
⦁ Recognize questions that can be answered by scientific experimentation
⦁ Define hypothesis and be able to write a good hypothesis
⦁ Understand and be able to identify the different variables in an experiment
⦁ Design and carry out a controlled experiment
⦁ Analyze data, form conclusions, and report findings to peers
Introduction:
The scientific method outlines a process used to solve a problem or answer questions about a natural event. (It is important to remember that certain types of questions cannot be answered by science.) One scientist may not follow the guidelines of the scientific method in exactly the same way that another scientist does, but some form of the process is used in any scientific study. (Belk and Maier, 2012). One version of the steps of the scientific method is shown below (Figure 1).
Data Collection
Uses your senses
Made with instruments and measurable
Part 1: Defining the Question and Writing a Hypothesis
Humans are by nature, curious about the world they live in. Scientists will study previous research and use their own observations of natural events to define a question to be answered. A good scientific question is one that is based on naturally occurring phenomena and has elements that can be tested. Place a check beside the questions below that can be answered scientifically.
⦁ Are GMO’s (genetically modified organisms), such as corn or fish, safe to eat?
⦁ What is the function of quills on a porcupine?
⦁ Does the full moon cause an increase in immoral acts?
⦁ Does lack of sleep in college students cause a decline in IQ and memory over time?
⦁ Should abortion be regulated by law?
The hypothesis is a proposed explanation of what has been observed. Often called an “educated guess”, a good scientific hypothesis is one that is both testable and falsifiable. (Belk and Maier, 2012) . Even though the hypothesis can be proven false, it cannot be proven true. Data from a particular investigation can only support the hypothesis. This evidence is added to the previous body of knowledge about the phenomena and strengthens the confidence in the hypothesis. Write a testable hypothesis for each of the questions above (only those you decided were good scientific questions) Phrase these in the form of if…then statements, e.g. “if (specific action is taken), then (this specific result is expected).
Part 2: Designing an Experiment
An important skill for you to learn in this course is how to design an experiment. It is essential that you be able to identify the variables involved in an experiment. A variable is anything which may be expected to change in the course of conducting the experiment.
Dependent variable(s): what the researcher will measure, count, or observe during the experiment. Suppose Sue wants to determine which type of fertilizer will be best for her roses. She could measure plant growth, number of blooms, size of blooms, etc.
Independent variable: the one variable the researcher deliberately changes during the experiment. This variable is expected to have an effect on the dependent variable(s). What is the independent variable in the experiment involving Sue’s roses?
Standardized variable(s): (other terms used include controlled variables or constant variables). These are variables which the researcher must hold constant in order to eliminate any effects they may have on the dependent variable(s). In the case of Sue’s roses and the fertilizers, standardized variables would include things like amount of sunlight, moisture, type of soil, size of pot, etc.
Experimental Design
NOTE: Remember, an independent variable does not change as other variables change, while a dependent variable does change as other variables change. To keep these straight, insert the variable names into this sentence in a way that makes the most sense: (Independent variable) causes a change in (Dependent Variable) and it isn’t possible that (Dependent Variable) could cause a change in (Independent Variable).
Identify the dependent and independent variable in each of the examples below:
1. Number of rosebuds opening is recorded each day for 2 months (see Sue’s roses previously where you already identified the independent variable).
2. White mice are fed a treat every time they manage to ring a bell. The time required for the mice to learn the task is measured.
3. The diversity of fish in a stock pond is measured before and after the introduction of nitrogen fertilizers (such as would occur when excessive fertilizer is used on crops).
4. Batches of radish seeds are subjected to radiation in a microwave oven for 15 sec, 30 sec, 45 sec, and 60 sec. The seeds are then allowed to germinate and the percentage of successful germination is recorded.
Part 3 – Experimental Analysis
1. Mr. Bossman, a supervisor at a manufacturing company, recently attended a professional conference and heard of a special energy drink that is reported to increase the productivity of factory workers. Mr. Bossman wanted to know if the claim was valid. He created two groups of 100 workers each and gave them the task of putting together a small control device his company manufactures. The workers were already familiar with the task, so it was not necessary to teach the task before beginning. Group #1 was given the energy drink before the task and Group #2 was not given the drink. Mr. Bossman then had his trusted assistant, Jane, count how many correctly assembled devices each group produced in the allotted time. Group #1 assembled 182 devices and Group #2 assembled 271 devices.
a. Identify the following:
Independent variable: Dependent variable:
Name at least two standardized (constant) variables:
b. Which group would be the control group? Why is it necessary to have a control group?
c. What conclusion could Mr. Bossman reach based on the results of this experiment?
d. Give at least two ways this experiment could be improved.
Part 4 – DATA REPRESENTATION
Generally, line graphs work best for continuous data, whereas bar graphs work best for categorical data. Remember, there are exceptions to every rule, but these are some broad rules of thumb. Continuous data is quantitative, you cannot count the number of different values. This includes data like sales, height, profit, etc. It can also include time, although time can be both continuous and categorical data. Bar graphs are great representations of categorical data, in which you can count the number of different categories (such as product type, gender, age group, etc.).
Consider the information included in Table 1 below and determine whether it represents continuous or categorical data. This will dictate the best way to plot the data.
The experimental setup consists of two (2) culture plates, each containing a different type of bacteria, either Bifidobacterium. longum or Bifidobacterium. pseudolongum. After a period of growth, the number of cells of each type are recorded as Log10 Cell Count per mL culture. The researcher then adds a set amount of the antibiotic ampicillin to each plate and measures the number of cells in each plate at various time points. Table 1 represents the data recorded for this experiment.
⦁ Identify the dependent and independent variables
⦁ Plot the information in the table below on the grid provided
Table 1
Time Post Antibiotic Addition B. longum B. pseudolongum
0 hr 9.4 8.7
5 hr 9.3 7.9
10 hr 9.0 7.7
25 hr 9.1 7.8
50 hr 10.3 7.5
Items to ALWAYS incorporate in a graph/plot:
i. TAILS = Title, axes, interval, labels, scales.
ii. Dry Mix = Dependent/responding variable on Y axis and Independent/Manipulated on X axis
⦁ List at least three things that make a good plot.
REFERENCES:
Belk, C. and Maier, V. Borden. Ch. 1: Can science cure the common cold? Introduction to the scientific method in Biology: Science for Life with Physiology, 4th ed., Boston: Pearson Education, Inc. publishing as Benjamin Cummings, 2012
Dickey, J. The Process of Scientific Inquiry in Laboratory Investigations for Biology 2nd ed., San Francisco: Pearson Education, Inc. publishing as Benjamin Cummings, 2002
Morgan, J.G. and Carter, M.E.B. Lab Topic 1: Scientific Investigation in Investigating Biology, 4th ed., San Francisco: Pearson Education, Inc. publishing as Benjamin Cummings, 2002
Patterson, J. L., Graybiel, A., Lenhardt, H. F. and Madsen, M. J. 1964. Evaluation and prediction of physical fitness, Utilizing modified apparatus of the Harvard Step Test. Am. J. Cardiol. 14: 811-827. DOI: 10.1016/0002-9149(64)90009-8.
Newton, D.F, Macfarlane, S, and Macfarlane G.T. 2013 Effects of Antibiotics on Bacterial Species Composition and Metabolic Activities in Chemostats Containing Defined Populations of Human Gut Microorganisms Antimicrob Agents Chemother 57(5): 2016-2025 DOI: 10.1128/AAC.00079-13
Websites:
http://www.topendsports.com/testing/tests/step.htm
http://www.sparkpeople.com/resource/fitness_articles.asp?id=1115
