How To Write a Scientific

Lab Report

By Sharon Reichard

An Interactive Tutorial

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Objectives

When you are finished this tutorial, you will be able to:

Document your findings and communicate their significance

Describe the report's format and basic components

Write a lab report successfully

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Purpose of a Lab Report

Persuade others to accept or reject hypotheses by presenting data and interpretations.Detail data, procedures, and outcomes for future researchers.Become part of the accepted body of scientific knowledge when published unless later disproved.Provide an archival record for reference and document a current situation for future comparison.

A formal lab report is essentially a scaled-down version of a scientific paper, reporting on the results of an experiment that you and your lab partner(s) have carried out. As such, the key sections of the report are directly analogous to the sections of a formal scientific paper.

A good lab report does more than present data; it demonstrates the writer's comprehension of the concepts behind the data. Merely recording the expected and observed results is not sufficient; you should also identify how and why differences occurred, explain how they affected your experiment, and show your understanding of the principles the experiment was designed to examine.

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Format of the Lab Report

It is extremely important that you understand the need for, and format of, a good report. Scientific work of any sort is useless unless its results can be communicated to others. You need to organize your ideas carefully and express them coherently.

Generic Outline of a Lab ReportI. Title Page

II. IntroductionIII. Hypothesis

IV. Methods & MaterialsV. Procedures

VI. ResultsVII. DiscussionVIII. ConclusionIX. References

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Format of the Lab Report: Title Page

The Title Page states the focus of your experiment. The title should be to the point, descriptive, accurate, and concise . If your instructor requires a separate title page, include the title followed by the name(s) of the project participant(s), class title, date, and instructors name. If a title page is required, consult your instructor about the specific format for the page.

TITLE PAGE EXAMPLE

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Concise title

Instructor’s name

Student’s name

Date

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Writing a laboratory report is as important as taking data. This includes the careful analysis of data and attention to the details of how the information is formatted for the ultimate reader. Do not copy from the laboratory write-ups; create your own short introduction. Be sure to cite your sources if applicable. The introduction should be concise. It should explain the outlines of the experiment, what results have been determined, and salient points about the experiment. It should be about how your experiment worked, not some reprise of the general statements in the write-ups. Remember that an introduction tells the reader what he/she is going to be reading.

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Format of the Lab Report: Introduction

INTRODUCTION EXAMPLE

Quick ReferenceMust Have:• Purpose of the experiment• Important background and/or

theoryMay include:• Description of specialized

equipment• Justification of experiment's

importance

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What Is a Real Hypothesis?A hypothesis is a tentative statement that proposes a possible explanation to some phenomenon or event. A useful hypothesis is a testable statement which may include a prediction.

When Are Hypotheses Used?The key word is testable. That is, you will perform a test of how two variables might be related. This is when you are doing a real experiment. You are testing variables. Usually, a hypothesis is based on some previous observation such as noticing that in November many trees undergo color changes in their leaves and the average daily temperatures are dropping. Are these two events connected? How?

Hypotheses contain two variables. One is “independent” and the other is “dependent.” The independent variable is the one you, the “scientist” control and the dependent variable is the one that you observe and/or measure the results. In the statements above and

HYPOTHESIS EXAMPLES:If  skin cancer is related to ultraviolet light , then  people with a high exposure to UV light will have a higher frequency of skin cancer.

If  leaf color change is related  to temperature , then  exposing plants to low temperatures will result in changes in leaf color.What is the dependent variable in the examples above?the dependent variable is underlined = skin cancer, leaf color

What is the independent variable in the examples above?the independent variable is underlined and italicized= ultraviolet light, temperature

Format of the Lab Report: Hypothesis

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This section of your lab report involves producing a written description of the materials used and the methods involved in performing your experiment. You should not just record a list of materials, but indicate when and how they were used during the process of completing your experiment.

The information you include should not be overly detailed, but should include enough detail so that someone else could perform the experiment by following your instructions.

Format of the Lab Report: Methods & Materials

We stuck flies to popsicle sticks by pushing their wings into a sticky wax we rubbed on the sticks. Then we made a dilution series of glucose, maltose, and sucrose in one-half log molar steps (0.003M, 0.01M, 0.03M, 0.1M, 0.3M, and 1M) from the 1M concentrations of the sugars we were given. We tested the flies’ sensory perception by giving each fly the chance to feed from each sugar, starting with the lowest concentration and working up. We rinsed the flies between tests by swishing their feet in distilled water. We counted a positive response whenever a fly lowered its proboscis. To ensure that positive responses were to sugars and not to water, we let them drink distilled water before each test. See the lab handout Taste Reception in Flies (Biology Department, 2000) for details.

METHODS EXAMPLE

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Format of the Lab Report: Procedures

Experimental Procedure describes the process in chronological order. Using clear paragraph structure, explain all steps in the order they actually happened, not as they were supposed to happen. If your professor says you can simply state that you followed the procedure in the manual, be sure you still document occasions when you did not follow that exactly (e.g. "At step 4 we performed four repetitions instead of three, and ignored the data from the second repetition"). If you've done it right, another researcher should be able to duplicate your experiment.

PROCEDURE EXAMPLEStep 1: The required materials were selected and taken to the workstation. Step 2: beaker was filled with approximately 300 ml of distilled water. Step 3: The beaker was gently placed on the hotplate. Step 4: The thermometer was placed in the beaker and the initial temperature was recorded. Step 5: The hotplate was switched on to high. Step 6: The temperature was recorded every 2 minutes until 6 minutes after boiling began. Step 7: The hotplate was turned off and the materials were allowed to cool for at least 10 minutes before the equipment was dismantled.

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Format of the Lab Report: Results

The results section should include all tabulated data from observations during your experiment. This includes charts, tables, graphs, and any other illustrations of data you have collected. You should also include a written summary of the information in your charts, tables, and/or other illustrations. Any patterns or trends observed in your experiment or indicated in your illustrations should be noted as well. Graphics need to be clear, easily read, and well labeled (e.g. Figure 1: Input Frequency and Capacitor Value). An important strategy for making your results effective is to draw the reader's attention to them with a sentence or two, so the reader has a focus when reading the graph.

RESULTS EXAMPLEFlies responded to high concentrations (1M) of sugar by lowering their probosces and feeding. The threshold concentration required to elicit a positive response from at least 50% of the flies was lowest for sucrose, while the threshold concentration was highest for glucose (Fig. 1). Hardly any flies responded to saccharin. Based on the results from all the lab groups together, there was a major difference in the response of flies to the sugars and to saccharin (Table 1). When all the sugars were considered together, this difference was significant (t = 10.46, df = 8, p < .05). Also, the response of two flies to saccharin was not statistically different from zero (t = 1.12, df = 8, n.s.).

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Include Tables

Include Graphs

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Discussion is the most important part of your report, because here, you show that you understand the experiment beyond the simple level of completing it. Explain. Analyze. Interpret. Some people like to think of this as the "subjective" part of the report. By that, they mean this is what is not readily observable. This part of the lab focuses on a question of understanding "What is the significance or meaning of the results?" To answer this question, use both aspects of discussion:

Analysis Interpretations

What do the results indicate clearly? What have you found? Explain what you know with certainty based on your results and draw conclusions:

What is the significance of the results? What ambiguities exist? What questions might we raise? Find logical explanations for problems in the data:

Since none of the samples reacted to the Silver foil test, therefore sulfide, if present at all, does not exceed a concentration of approximately 0.025 g/l. It is therefore unlikely that the water main pipe break was the result of sulfide-induced corrosion.

Although the water samples were received on 14 August 2000, testing could not be started until 10 September 2000. It is normally desirably to test as quickly as possible after sampling in order to avoid potential sample contamination. The effect of the delay is unknown.

Format of the Lab Report: Discussion

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Format of the Lab Report: Conclusion

The conclusion is alot like the introduction except, instead of a summary of what you are going to do, it's a summary of what you did. The reason you have a conclusion is because your lab report might be long and the reader may not remember all the important points that you stated. Also, it gives you a chance to explain anything that might have gone wrong or could be improved, as well as propose future experiments. Like the introduction, it should be short and to the point.

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CONCLUSION EXAMPLE:It was determined from the data plotted in the temperature versus time graph (Figure 2) that the boiling point of water is 99.51 C. This concurs very closely with the stated hypothesis, therefore the experiment was deemed a success. The percent error was found to be 0.49%. Possible sources of error could have involved impurities in the water and human error in reading the thermometer. Possible sources of error may be impurities in the water which may be chemicals from dirty glassware. Improvements would include more accurate thermometers, clean equipment and proper reading of the thermometer. 1. What you found2. What you think3. Errors (speculation)

Quick ReferenceMust do:• State what's knownMight do:• State significance• Suggest further

research

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ReferencesIn the body of the lab report itself, a citation normally consists of the last name(s) of the author(s) and the year of publication (Randolph, 1998). This is then expanded upon in your References section. This is a must whenever you cite a source within the body of text so the reader knows immediately where you acquired your information.

In the References section at the end of your report, you will list any books, publications, or web sites you cited in the report.

List only those works you have actually referenced in the scientific paper. Remember, this is not a bibliography, which would involve listing books and other works you reviewed but did not find necessary to include in your report because they did not specifically pertain to your study. Therefore, a References section includes only those works you refer to in the text itself.

REFERENCE EXAMPLEList names alphabetically by last name, as well as the year of publication, title, publisher location, and publisher, as follows:Randolph, M. (1998). How to write proper references for Lab Reports. New York: Academia Press.

Format of the Lab Report: References

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No that you have read this interactive tutorial, you are ready to prepare your formal lab report.

General lab report format tipsNothing makes a lab report appear less convincing than misspelled words, so make sure you read and re-read your report before submitting it to your professor or for publication. You want readers to believe in your ability and the knowledge you have gained. A lab report or scientific paper illustrates all the hard work you have done; therefore, showcase that work in a well-written, professional style! 

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