# Notes on Lab Reports

• By popular request, here are some notes about how to produce a good lab report for 1311.

• There are five parts to a lab report. The idea is to learn how to write a clear and understandable report that conveys all necessary information.

• Abstract: Here's where you lay out the goal of the exercise. Outline what you will do and what you will use to do it. It's an outline of what the exercise is all about. For example,
```   We are going to study swiss cheese.
```
isn't going to do it. You need to give details, like
```   We are going to study swiss cheese using a ruler and magnifier
to investigate the holes and slice thickness.  We will taste
the flavor and weigh samples to measure density compared to
cheddar chesse.
```
This is much better. Now we can read what the whole idea is.

• Measurements: This part will vary each week, depending upon what we are doing. The important thing is to be careful in making the measurements. Most times you will be using rulers to measure lengths or distances.

• Analysis: In this part you will do something (usually some calculation) with the measurements you made. The calculations will be described in the lab book, so read the description carefully and be sure you are doing it right. Do your scratch calculations on a piece of scratch paper so you don't mess up your lab report.

• Error Analysis: Here we want you to think about the causes of the measurement error you encountered. Very important: never use the term "Human Error"! Look for the actual physical reasons for the variation in measured values. Also remember: goofs such as calculation errors, not measuring the right thing, and so on, are NOT the kind of measurement error we are talking about.

For example, there is zero-setting error. On a ruler, the scale lines have some visible width. For absolute consistency you must always measure from the same side of the scale line. Let this vary and you can introduce a fraction of a millimeter error. Another possibility: if you are trying to measure the diameter of something that is circular, you must get the ruler precisely across the diameter. An error in placing the ruler will result in a measured value that is too small.

The reason for not using the term "Human Error" is simply that it doesn't say anything. It means that you really don't understand what the errors really are.

• Conclusions: Here we want to read what you learned from doing the exercise. Don't simply recount what you DID - we know that already. What did you find out about measurements or the subject that you didn't already know? Good conclusions really say something and are more than one or two sentences long. Consider the swiss cheese.

```   We measured the size of all the holes we could locate and tabulated
the sizes.  We found the average size to be about 1 cm.  We next
tasted the swiss and a piece of cheddar.  They are not the same.
We weighed a cube 4 cm on a side and recorded its density.  It
is not as dense as a 4 cm cube of cheddar cheese.
```

This recounting of what you did is, ahem, not going to cut the cheese. We know what you did already. The instructor wrote the lab book! Write down what you learned about cheese.

```   We learned that swiss and cheddar have very different flavors.  That
must come from different processes used to make them.  The holes
did not vary in size as much as I thought they did.  The holes must
result when the cheese ferments and releases gas, which makes bubbles.
The bubbles make the cheese less dense than cheddar, so you get less
cheese in a given volume, or, a pound of swiss is bigger than a pound
of cheddar.
```

Not quite so cheesy (sorry) as the simple description of procedures. This shows some insights into the properties of the cheese.

If you have any other suggestions for things to include here, please tell me.

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