Physical Science Lab – Accuracy v. Precision in Measurement
Discussion:
In this activity, you will drop a crayon and see how accurately (or should I say precisely?) you can hit a target. You will need a group of 2 bright young scientists (a "shooter" and a "coach") for this activity.
Equipment:
Each group will need:
5 paper targets (2 per person, plus an "extra")
crayons
tape
Procedures:
Part 1 - Eyes Open:
1. Place the target sheet #1 on the floor.
2. The "coach" kneels down near the target and catches the crayon after it hits the target the first time making sure that a visible mark was made.
3. The "shooter" holds the crayon about 2 meters above the floor (approximately
level with the top of your head), and drops it on the target. The goal is to score a "bulls eye".
4. Repeat step 4 for a total of 10 trials (drops)
5. Label the sheet with the shooter's name and "Eyes Open".
6. Replace the lower sheet with a new target. The next person in the group becomes the shooter.
7. Repeat so that both people in the group has been the "shooter".
Part 2 - Eyes Closed:
1. This part of the activity works pretty-much the same as the first part, except that the person dropping the crayon must keep their eyes closed at all times. (!). One person in the group drops, one catches. The catcher may “coach” the “shooter”
2. After the you take 10 shots at the target, label the bottom target with your name and "Eyes Closed".
3. Switch roles so that each person in the group is a "shooter" and a "catcher"
Name ______Pd ______Date ______
Safety Precautions
Results:
- Suppose that the target's bulls eye represents the actual value of some unknown characteristic (for example: your height in meters)
- each of your "shots" in this activity represents a measurement of some
quantity (for our example: your height measured by some means)
Data: Accuracy and Precision
Zone 1 shots / Zone 2 shots / Zone 3 shots / Zone 4 Shots / Zone 5 ShotsEyes Open
Partner 1
Eyes closed
Partner 1
Eyes Open
Partner 2
Eyes Closed
Partner 2
Analysis:
Like any other physics terms, accuracy and precision are carefully defined, and may not mean the same thing to a scientist as they do to a non-scientist. Before you go on, be sure that you understand the meanings of the terms accuracy and precision.
1. For each of your (two) targets, write a brief description of the pattern of "shots" using the terms "accuracy" and "precision".
Were your results accurate?
Were your results precise?
Why do you think so?
2. For each of the descriptions below, make a sketch of a target and a group of "shots" that could be described as: (attach your sketches to your final draft of your lab write up)
a. very accurate and very precise.
b. very accurate, but not very precise.
c. precise, but not very accurate.
d. neither precise nor accurate.
3. Do you think accuracy or precision is most important in testing a hypothesis? Why?
4. Give at least two examples of how you could increase the precision of your measurements in an experiment.
5. Give at least two examples of how you could increase the accuracy of your measurements in an experiment.
Write up this lab using the lab write up requirements handed out in class. Make sure to attach your targets to the write up (all good scientists keep their original data).