InLab: the lab experiment
1. Setting up the lab:
Before you start the lab, review the objectives
and procedures you will follow. Take notes as you set up your experiment
and calibrate instruments to help you document your experimental protocol
so that you may use it later when writing the Methods section of your
lab report.
On a sheet of paper or in your lab manual or in
a formal lab
notebook, list the lab materials you'll be using and describe the
set-up for this experiment. Take notes about potential sources
of uncertainty so that you may refer to them when you are writing
the Discussion section of your lab report. You may want to or may be
required to draw and label the instrument(s) you'll be using.
Click here to see an example of lab
notebook pages.
2. Getting ready to collect data:
Before you start collecting data, you need to reconsider
the whole point of the lab procedure: to determine whether or not your
hypothesis is supported by the data from the experiment. Revisiting your
hypothesis and gathering information about the data you will be collecting
will help you to better understand your data as you are collecting them.
It will also help you to organize your data in a table or spreadsheet.
- Review and restate the hypothesis
you are testing and the variables involved. This may be a good time
to refer to your PreLab. If you haven't completed a PreLab, create
a hypothesis now before you start the lab procedure.
- List the variables
in the experiment, noting which are independent and which are dependent.
Refer to your PreLab if you have completed it.
- Next to each variable, write the units of measurement you will use
in the lab. Noting the unit
of measurement for each variable will help you to be sure you
are recording the data correctly.
- Determine whether or not you have control
and treatment groups in this experiment. Determining whether or
not your experiment uses control and treatment groups will help you
to structure your data so that you can see more clearly the relationship
between those two groups.
3. Preparing a table or spreadsheet for recording your data:
Using the information you have gathered about the data you will be collecting,
create a raw data table or set
up a spreadsheet for entering your data. (If your lab manual already
has a table for the data, skip this step.)
For help in determining which you should create now, a table or a spreadsheet,
click
here. For general information on tables, go to Designing
Tables.
4. Conducting the experiment:
Carefully follow the experimental protocol. As you conduct your experiment
and record your data, take notes on what you are doing and on any changes
in your procedure. Also, describe in writing or sketch out on a sheet
of paper your observations as you collect data during the experiment (observations
are potentially significant things that are not reflected in the measurements:
color, smell, interesting reactions, unexpected behaviors, etc.) As you
record your data, take note of any trends emerging in the data.
Taking good notes will help you recall the experiment later on when
you are writing your lab report. It's also important to note any problems
with the procedure or deviations from the established protocol. Even
if you are following the protocol in a lab manual, sometimes you will
set up and run things differently.
As you record your data, you should be asking yourself various questions:
What are the relationships
among the variables? Do the data behave in the way that you had
anticipated? If not, why not? If the data make no sense, you may need
to consider sources
of uncertainty once again. Sources of uncertainty may affect the
accuracy
and precision of your experimental data. For more information on
statistical calculations and graphical display of uncertainty, see the
graphing tutorial on Using Error
Bars in Graphs.
5. Visualizing the data:
Now that you have entered your data in a table or spreadsheet, you are
ready to represent the data in the appropriate visual format for your
lab report. Representing your data in a visual format will allow you to
identify trends and relationships among variables more easily. Follow
these steps:
- Establish what types of data you have, quantitative
or qualitative.
- Determine if the data should be represented as a table
or a graph.
- If you decide to use a graph to represent your data, determine which
type of graph is one that
best represents your data.
- If a table is the best format for representing your data, then modify
the table you used to collect your data so that it is labeled and
organized properly. Go to Designing
Tables for help on making tables.
- If you need help creating a spreadsheet to make a table or graph,
go to Excel Tutorial.
- Remember that the purpose of your table or graph is to summarize
your findings for yourself and for others and to reveal trends in
your data.
6. Making sense of your data:
Review all your data--tables, graphs, and drawings--and try to make sense
of the overall findings of the lab procedure. Summarize the overall findings
in a sentence or two. If your lab instructor says it is permissible, compare
your findings with those of other students in the lab.
Summarizing your data in a sentence or two helps you to understand
the lab. It is also useful for when you write the Results section of
your lab report.
Corroborating data or sharing findings is a very common practice among
scientists, which usually leads to more ideas and experimentation. For
this reason, comparing your results to other students' results can be
valuable as a way of testing your findings. It's OK if your findings
are different. Your job is to try to figure out why, to identify the
sources of the difference. You can use this information when explaining
your findings in the Discussion section of your lab report.
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