• American Public University

• CHEM 133  Lab 1- Experiment 1 - Accuracy and Precision - OER PART 1

Lab 1: Accuracy and Precision (How Good of a Shot are You?)
PROCEDURE
Part 1
1. Find three sheets of paper. It doesn’t matter what size they are, as long as you have three pieces that are the
same size. Wad each of them up into a “ball.” These will be your projectiles for this experiment.
2. Mark a small target at which to throw your projectiles (i.e. a bull’s-eye). It should be on a flat surface that makes
it easy to mark their position. The floor works well, or maybe a table top.
3. Take three shots at your target from a distance of your choice (make it challenging, and it will be more fun!).
Measure and record the distance in inches (Table 1) from the center of your target to each of your projectiles.
This reflects your accuracy. Do not move your projectiles, as you need leave them where they are for the next
step and the next measurement.
4. After measuring your accuracy, make a label with your name, the lab title, and the date, and place it next to
your bull’s-eye. Unless all three—your name, the lab title, and the date are on the label, in focus, and legible,
you will not receive credit. Take a picture of your results (the location of your shots relative to the bull’s-eye),
and make sure your label can be read clearly in your picture, your bull’s-eye is clearly visible, and all three shots
are also clearly visible. Save this single picture in a PDF document in order to submit it in the Lab 1 Assignment.
Follow the link if you need assistance. If you do not submit your pictures in PDF format on the Assignment, you
will not receive credit.
5. Use a piece of string or a ruler (or anything you want, really) to find the smallest circle that will enclose the final
position of all three projectiles. Measure and record the diameter of this circle in inches (Table 1). The circle
will have at its center a point between the three projectiles, and it will likely not be the center of the bull’s-eye.
The size of this circle reflects your precision.
6. After measuring your precision, make a label with your name, the lab title, and the date, and place it next to
your circle. Unless all three—your name, the lab title, and the date are on the label, in focus, and legible, you
will not receive credit. Take a picture of your results (your shot grouping), and make sure your label can be read
clearly in your picture, and the grouping of all three shots is also clearly visible. Save this single picture in a PDF
document in order to submit it in the Lab 1 Assignment. Follow the link if you need assistance. If you do not
submit your pictures in PDF format on the Assignment, you will not receive credit. This applies to all labs going
forward.
7. Find two other people to do the experiment as well—each taking three shots from the same distance as you
did. Record the same measurements for accuracy and precision (Table 1). You do not need to take pictures of
these trials.
Table 1. Accuracy and Precision