LAB REPORT
GUIDELINES
APPENDICES
GUIDELINES FOR WRITING LABORATORY REPORTS
The purpose of written laboratory reports is to teach you to present an experiment in the accepted scientific format. This format is used to present research in all fields of science, and can be found in any scientific journal.
Title
You may use the title of the experiment, which is given in the laboratory manual.
Introduction
The “Introduction” is used to put the reader into perspective. Typically, the writer should describe some of the experiments that have been done. , followed by a description of the current status of the problem, and concluded with a brief statement about what is proposed, which could be a description of the nature of the problem being investigated and the hypothesis to be tested.
Materials and Methods
The equipment and materials used should be incorporated into the text and not listed separately. It is not necessary to include trivial items such as "ink" and "paper" for the physiograph.
The "methods" should be a complete description of what was actually done (in the past tense, passive voice using complete sentences). Try to avoid using the personal pronouns "we" or "I". Thus, instead of saying: "We struck the turtle on the head." you could state, "The turtle was sacrificed by a blow to the head.".
DO NOT COPY directions from the laboratory manual. The procedure you used may differ from what the laboratory manual states. To help in writing your report, take careful notes of your methods during lab. Your report should provide sufficient detail so that someone else could follow your methods and repeat the experiment. This procedure is extremely important in writing scientific papers. However, it is not necessary to include trivial details such as, "The physiograph was plugged in and turned on.". You may assume that the reader is intelligent enough to know this.
Results
Your results and observations should be described and documented. Examine your data and determine the method best suited for its presentation. The documentation generally is presented as Tables or Figures (e.g. graphs, drawings, and photographs). Tables should be preceded by a caption that describes what the table is about. For example:
Table 1. Effect of temperature on turtle heart rate.
|
Temperature |
Turtle Heart |
|
of Ringers (°C) |
Rate (beats/min) |
|
10 |
15 |
|
20 |
25 |
|
30 |
40 |
Captions should be placed at the end of a figure. If the figure is a graph, the "X" axis (independent variable) and "Y" axis (dependent variable) should be of approximately equal length, and should be labeled with appropriate units (see below and following section titled "Graphs").
Fig.1. Effect of temperature on turtle heart rate.
A properly prepared table or figure should be interpretable without reference to the body of the text.
Whenever possible, make data quantitative. For example, a physiograph recording can be made quantitative by counting the number of events per unit time, or by measuring the amplitude (height) of a recording. "Raw" data are seldom used directly, but are refined mathematically. For example, data from a number of observations might best be reported as the mean ± the standard deviation. One can also analyze results statistically to determine significance of any differences among means. Do not show your rough calculations unless they are critical to understanding results. You may, however, include them in an "Appendix" at the end of the paper for reference. Finally, you should tell what you think your results mean in the written text of the "Results" section.
Discussion
In this section, tell how your results compare to what others have reported in the literature, and tell what the scientific implications are. Be specific in discussing your results. For example, do not merely state, "Obviously the heart rate is influenced by temperature". Instead you could state, "As temperature increased, heart rate increased". This statement could then be followed with a discussion of why this phenomenon occurs and the possible advantages it might have to a "cold blooded" (poikilothermic) animal such as a turtle.
Occasionally "unexpected" results are obtained. These results must be dealt with scientifically. Never assume your data are "wrong" just because they deviate from what was "expected". "Right" and "wrong" are judgmental terms that should not be applied to experimental data. However, you may have made an error in technique, the subject or animal may not have cooperated or the equipment may not have been functioning properly. If you suspect such a problem, discuss it and state how it could have been corrected or avoided. In any case, deal with the problem objectively and "matter-of-factly", and do not engage in self-criticism.
Finally, use the author-date system of citing references: "According to Jones (1983) turtle heart rate increases as temperature rises", or "Turtle heart rate increases as temperature rises (Jones 1983)". If an article or book has 3 or more authors, use the first author's last name and "et al." instead of the other authors' names. Do not pad your discussion with long quotations.
Conclusions
List numerically as conclusions the major deductions evident from your results. Do not confuse results with conclusions. For example, if you observe that a subject's blood agglutinates in Anti-A antiserum, but not in Anti-B antiserum, you would report in "Results" that the subject has type "A" blood, but you would "conclude" that the subject has type "A" antigens on his red blood cells.
Literature Cited
List references used in the preparation of your paper alphabetically according to the last name of the first author. Examples are listed below.
1. Typical Journal Article
Jones, S.S. (1983) Effects of temperature on turtle heart rates. Amer. J. Physiol. 28:192-197.
2. Typical Book
Jones, S.S. (1983) Poikilotherm Physiology. 2nd Ed. Academic Press, New York. pp. 131-133, 144, 158-170.
3. Multiple Authors - List all authors
4. Multiple papers in a single year by the same author(s) - Use "a", "b", etc. after the date (e.g. 1983a).
5. Edited Text
Jones, S.S. (1983) Turtles. In Poikilotherm Physiology (Edited by Swiveltisch, A.S.), pp. 191-198, 201. Academic Press, New York.
GRAPHS
Graphs (called figures) picture numbers and number relations for the scientist by showing the dependence of one property upon another. You will be expected to draw a number of graphs based upon your experimental data. Because of some small experimental error, points on your graph will seldom fall exactly on the curve expressed by the graph. The more accurate the data, the closer the fit to the curve.
Whenever you construct a graph, keep the following in mind:
1. The independent variable should be plotted on the x-axis (abscissa), and the dependent variable should be plotted on the y-axis (ordinate). The values of the dependent variable automatically change as the values of the independent variable are arbitrarily changed.
2. It is not necessary to start from zero origin when drawing the scale. For example, if your data on the x-axis start at 50 units, and the y-axis start at 25 units, it would be acceptable to make the origin 48 and 24 units, respectively. However, it is often more informative to begin with zero at the origin.
3. It is not necessary to choose the same scale of units on both axes. For example, each division on the x-axis might represent 2 units, while each division on the y-axis could represent 4.
4. The graph should be planned to cover as much of the sheet of graph paper as possible. By choosing wide divisions between units, more accuracy is obtained. NEVER DRAW A 2 X 2 INCH GRAPH ON 8 X 10-INCH GRAPH PAPER.
5. Connect the points on the graph with a French curve or draw a curve that best follows the "trend" of the data.
LOGARITHMIC FUNCTIONS AND SEMILOG PAPER
In many cases, the dependent variable changes logarithmically when the independent variable is arbitrarily varied arithmetically. Thus, the logarithm of the dependent variable must be plotted instead of the arithmetical data. Since it sometimes becomes tedious to compute logs or look them up in a table, the graph may be plotted on a special kind of paper called semilog which automatically plots the logarithm for you.
On semilog paper, the y-axis is divided into a logarithmic scale rather than the arithmetical scale found on the x-axis. (On log-log paper, useful in some instances, both axes are divided into log scales.)
Usually a sheet of semilog paper will contain from two to four cycles on the log portion. Each cycle corresponds to the characteristic of the log of the number being plotted, while the subdivisions within the cycle correspond to the mantissa of the logarithm of the same number.
