Lab Report Guide Overview Purpose When scientists make discoveries, they write r

Lab Report Guide
When scientists make discoveries, they write reports to share their discoveries with the world. Likewise, after you complete an experiment, you can write a report to share what you discovered.
Writing a lab report is an important skill because it helps you demonstrate what you learned in a science experiment. It also helps you practice writing accurately and clearly about technical things—a skill that is valuable in the real world.
This guide describes the format and style of lab reports. It has many tips that will help you write stronger lab reports. Use it as a reference throughout your science studies.
Lab Report Format
Although lab reports vary somewhat in format, they typically include all of the components below, in the order shown:
Science Writing Style
Science writing is different from other styles of writing you may know, such as persuasive and narrative writing. As with all types of writing, science writing has its own style. Its main features are that it is precise and avoids bias.
Science writing is precise. While being concise, use descriptive language and specific details to help readers who did not make the observation “see” what you observed. For example, below are two alternatives to writing “The liquid had bubbles” that are more precise:
 “The liquid had small bubbles the size usually seen in soda”
 “The liquid produced bubbles the size of grapes or marbles.”
Science writing avoids bias. Be sure to use objective language, avoiding subjective descriptions such as “The liquid had huge bubbles.” Also, write using the third-person voice so that you can put the science topic in the starring role. By avoiding personal pronouns such as I, we, you, he, she, and they, science writing allows readers to focus on the science topic, undistracted by thoughts about the person who did the work.
Page #
Part 1
Introduction (Title, purpose, question, hypothesis, variables)
Part 2 Part 3 Part 4
Materials and Procedure 4 Data (Table and Graphs) 5 Analysis and Conclusion 6
Writing this way takes practice for most students. At first, your writing may feel and sound formal or stiff. But in time, your writing will become clear and precise.
Follow this format throughout this course. The remaining pages of this guide explain how to write each of the above sections of your lab report. At the end, there are also:
 Tips for Using Your Student Guide and the Lab Lesson
 Lab Report Checklist
Part 1: Pre-Lab Information
Title your lab report with a few words that summarize the lab investigation.
The lab report should begin with one or two sentences that state the purpose of the investigation—what you want to see, practice, learn about, or test. The purpose statement answers the question “What are you trying to find out by doing this experiment?”
The three most common types of labs are:
 inquiry labs: you measure how changing one variable affects another variable
 discovery lab: you see a scientific phenomenon—perhaps for the first time.
 forensic lab: you gather and analyze data as evidence to build an argument in response to a question, as in a court case.
All three types of labs give you an opportunity to learn important scientific skills and concepts.
At its core, science is about inquiry—the act of asking questions and seeking answers. Most labs begin as the result of a question, and the pre-lab information of your lab report should include a question. For example, you may have noticed that you seem to play basketball better at the court in the park than you do at home in my driveway. After doing some thinking and research, you realize that the surface of the court at the park is different than your driveway. As a result, you might formula a scientific question, “What is the effect of the court surface on the height that the basketball bounces?” To answer this question scientifically, you could perform several experiments and gather data.
Hypothesis (or Prediction)
A hypothesis (or prediction) is an initial answer to a question—a possible explanation or expectation based on prior knowledge or research. Before most labs, you will formulate a hypothesis (or prediction), and it should be listed among the pre-lab information of your lab report.
A good scientific hypothesis states conditions, expected results, and possible reasons. For example, you could respond to the basketball question above with a hypothesis such as “If the court surface is smooth concrete like at the park, then the basketball will bounce higher, because smooth surfaces have better contact with the ball.” Like this hypothesis, hypotheses are often structured using the format “If … then … because…,” which is described below:
 The “If” portion of the hypothesis describes something that you will change in the experiment.
 The “then” portion of the hypothesis describes what you think will happen as a result of that change.
 The “because” portion of the hypothesis describes the reason why you think that change will occur. It should be much more than “because I think so.” It should state why.
This format clearly identifies the variables that must be measured when you test the hypothesis through an experiment. Generally, the lab lesson will provide guidance if an alternative to the “If… then… because…” format is appropriate for the prediction.
Lab Report Guide
Special Note about Inquiry Labs:
For inquiry labs, questions are generally structured “What is the effect of X on Y?” Hypotheses will generally be in the form “If X [describe how you will change X during the experiment], then Y will [predict how Y will change in response], because [give your reason].” In many inquiry labs the variables lend themselves to a scatterplot (X-Y plot).
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The last part of the pre-lab information section of your lab report should be a description of the variables. There could be up to four types of variables, described below:
 Independent Variable (IV): This is the factor that is directly manipulated in the experiment. Sometimes, you will also hear this called the manipulated variable. In the traditional format of “If X…then Y” for a hypothesis, the independent variable is X.
 Dependent Variable (DV): This is the observable factor that varies due to changes to the independent variable. Sometimes it is called the responding variable. In the traditional format of “If X…then Y” for a hypothesis, the independent variable is Y.
 Constant Variables: These are variables that could affect the dependent variable, but which you prevent from changing during the experiment. Holding other variables constant allows an experiment to focus on the relationship between the independent variable and dependent variable.
 Controls: Controls are treatments that provide a baseline for comparison. Controls are not used in every experiment, but they can be helpful for seeing what happens when a variable is unchanged or seeing what happens when a variable is changed in a specific (controlled) way that demonstrates a certain set of conditions. Having a control to compare your experimental conditions against allows you to see better what has actually changed.
In a lab experiment, you observe and measure variables against a scale. That scale can take many forms:
Quantitative Variables Scales are usually a pre- established numerical scale, such as centimeters, degrees Celsius, time, as measured using tools such as rulers, thermometers, and clocks. They can also be a count of the number of times something occurs.
Qualitative Variables Scales can be a descriptive scale created for the variable, such as a list of possible colors of paint chips. They can also be a pre-established set of options, such as physical change and chemical change or the three possible genotypes of a mouse’s fur color, BB, Bb, and bb.
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Lab Report Guide
Part 2: Materials and Procedures
List all the supplies you will need to conduct the experiment. Include the names of the materials, quantities, SI units, and even brand names if the brand may have affected your results.
Create a numbered list summarizing the steps you carried out in completing the lab. If you made any changes to the original instructions in the Student Guide (either upon the advice of your teacher or on your own) be sure to identify them. Describe each step with accurate, concise language so that someone who has never performed the experiment could repeat it. Be sure to include details about any
Part 3: Data (Tables and Graphs)
While doing the lab procedure, you collected data on a data sheet or in your lab notebook. Your lab report should display that data using formal tables and graphs. Use the descriptions below to choose the right displays to make your data clear to the reader and reveal what is important about the data.
Tables: Be sure to label each column and row in the headers. Quantitative data should include all measurements and calculations, including correct SI units of measurement. Make sure units are consistent and that you use an appropriate number of significant figures. For data that is qualitative, describe the things you saw, heard, felt, or even smelled during the experiment. (See the sections titled “Science Writing Style” and “Variables” for more guidance.)
Bar Graphs: Use these graphs for comparison of two or more sets of conditions or categories
Histograms: Use this type of bar graph to show the frequency of ranges of values.
Line Graphs: Use these graphs to show change in one variable as a second variable is changed. Typically, the individual data points are plotted, and then lines are added to show trends. A line segment
apparatus and materials that you used, especially if you made substitutions to the apparatus and materials described in the Student Guide for the lab.
Lab Report Guide
Trials: For some labs, you will repeat the experiment to collect additional sets of data. By performing additional trials, you can refine how you execute the lab procedure, increase accuracy, and avoid one-time results. Instead of performing additional trials, you also may be able to combine your data with the data of other students if you are all performing the same experiment.
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that connects two points on the graph provides a slope, which can have meaning as a rate of how one variable changes relative to another. This slope has a mathematical formula. These graphs can be very helpful when looking at changes over time.
Pie Graphs: These graphs are used to show parts of a whole or percentages.
Scatterplots: These graphs show each pair (X, Y) as a point in the coordinate plane. They differ from line graphs in that individual points are not connected to each other with one line sequentially. Instead the points express a trend. This trend can be calculated mathematically as a regression equation and correlation value that measures how closely the data follow the general trend.
In an inquiry lab, if the data is numerical, the X (independent) and Y (dependent) variables appear their usual places on the horizontal and vertical axes, respectively.
Part 4: Analysis and Conclusion
The analysis portion of your lab report should describe the data and results in words. You should:
 analyze and state the relationship between the independent and dependent variables describing how the dependent variable reacted to the change in the independent variable. If you used a control, you should compare to the control.
 explain all trends in the data, as well as any specific observations during the lab that were interesting.
 Describe specific data points that help explain the outcome of experiment
 Present and interpret statistics such as the range, variance, standard deviation, trend equation, or correlation.
 Interpret graphs with descriptions in words.
Background Research
Before you do an experiment, you usually have prior knowledge about the topic—things you learned from reliable sources such as your teacher, books, online resources, doing experiments in the past, etc. Sometimes, you may do a bit of this research before performing an experiment, and sometimes, you may do additional research after the experiment, before you write the conclusion of your lab report. Your teacher may provide specific guidance about what you should research, the type and number of sources you should use, when you should do the research, and how that research should appear in your lab report. Your teacher may also ask you to relate the experiment to another specific topic or context. Be sure to consider all of these things as you write your analysis and conclusion.
The conclusion portion of your lab report should explain your new understandings as a result of the lab experiment. It should also address the question that originally led to the experiment.
 Determine whether the hypothesis was supported. First, restate your hypothesis. A hypothesis is not an answer, so it cannot be described as “correct” or “incorrect.” Avoid this common error. Instead, state whether the hypothesis was “supported” or “not supported” by your results. Be sure to explain how and why you have made that conclusion.
 Identify possible sources of error. Scientific errors are factors that could have contributed to the uncertainty in the outcome of your experiment. Could measurements have been more accurate? Could you have performed more trials? Could environmental factors, such as the lab’s lighting or temperature, have had an effect? State these possible sources of error and analyze or estimate how much they may have affected your results.
Even if your hypothesis is not supported by the results of the lab, you can still produce an excellent lab report as long as you show a thorough understanding of the scientific concepts. This is often where your results are linked to your background research. You will explain your method, findings, and suggest revisions for future experiments. In this section, you should explain applications of the experiment describing how these findings or similar experiments could be used in the real world to benefit society. Lastly, you may also include any additional related questions you may want to explore in the future.
Lab Report Guide
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In an inquiry lab, the analysis and conclusion will focus on the relationship of X and Y.
Tips for Using Your Student Guide and the Lab Lesson
Besides this guide, you can also use the lab lesson and Student Guide. Here are some tips:
 Your lab report’s title should match the title of the lab in the Student Guide and in the online lesson.
 Your purpose statement may be inspired by the purpose statement that appears at the top of the first page of the Student Guide.
 Your lab question and hypothesis should be formulated during the Warm-up of the lab lesson. If you forgot what you wrote, you can revisit the Warm-up and copy, paste, and proofread your question and hypothesis.
 The variables are generally listed in the header of the student guide.
Lab Report Checklist
Pre-Lab Information
 Did you title your lab report?
 Did you state the purpose of the experiment?
 Did you state the question you posed before the experiment?
 Did you restate the hypothesis (or prediction) you formulated before the experiment?
 Did you list all variables, labeling the independent and dependent variables? Did you indicate any constants or controls?
Materials and Procedure
 Did you make a list of materials? Including quantities and SI units?
 Did you present the steps of the procedure as numbered list? Did you note any changes to the original procedure?
 The Student Guide usually provides tables for you to use for collecting data. The data table in your lab report can often replicate this format.
 The Instruction phase of the lesson usually includes tips from your on-screen teacher for learning how to fill in and interpret the data.
 The Student Guide may also provide you specific questions to consider as you analyze your results. Be sure to address them in the analysis and conclusion of in your lab report.
 If you are struggling with the lab report, your teacher has access to additional activities that will help you reflect on your lab experience.
Data—Tables and Graphs
 Did you organize all data in a clearly labeled table and/or graph?
 Did you check that your data is accurate and complete?
 Did you title any tables and graphs? Did you label rows, columns, axes, etc., and include units?
Analysis and Conclusion
 Did you interpret your data and graphs in the analysis, and not just restate your findings?
 Did you determine whether your data supported or refuted the hypothesis?
 Did you describe possible sources of errors?
 Did you suggest ways to improve or further your
lab investigation?
 Did you make sure your writing was precise, unbiased, and concise?
 Did you meet the content and format expectations of your teacher?
Lab Report Guide
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