Precision and Accuracy
Question: Do step-tracker devices measure steps accurately and precisely?
Materials:
Step-tracker apps and/or pedometers
Data Sheet
Purpose: We will use step-tracker devices to demonstrate an understanding of
precision and accuracy in scientific measurements.
NGSS Standards:
Practice 4: Analyzing and interpreting data
Practice 5: Engaging in argument from science
Form a hypothesis
Precision = the closeness of two or more measurements to each other -CONSISTENT
Accuracy = the degree to which the result of a measurement conforms to the
correct value -- CORRECT
Which device do you think will be the most precise? Which device will be more accurate?
Write your hypothesis as a sentence. Example: “Of the pedometer, Google Fit app, and
MyFitnessPal app, the Google Fit app will measure the number of steps most precisely and
accurately.” Use the most specific language you can in your hypothesis statement.
Collect data
Procedure:
1. Choose three step-tracking apps or devices.
2. While you carry each device, count the actual number of steps you are taking. Write the
number you counted in the blank next to actual steps.
3. Write the number of steps measured by the device in the blank next to measured steps.
4. Repeat for a total of 3 measurements for each device.
Device/App 1: ________________________
Actual steps _____
Actual Steps _____
Actual Steps _____
Measured steps _____
Measured Steps _____
Measured Steps _____
Device/App 2: ________________________
Actual steps _____
Actual Steps _____
Actual Steps _____
Measured steps _____
Measured Steps _____
Measured Steps _____
Device/App 3: ________________________
Actual steps _____
Actual Steps _____
Actual Steps _____
Measured steps _____
Measured Steps _____
Measured Steps _____
Calculations
How precise were the measurements of each device? We can calculate the range
of variation of measurements from each device. If the range is smaller, there is
less variation and the measurements are more precise.
To calculate the range of variation, subtract the smallest measurement from the
largest measurement from each device. Record your results below.
Range = Largest measured steps - Smallest measured steps
Device/App
Range
How accurate were each device’s measurements?
To calculate percent accuracy, first subtract the measured steps from the actual
steps. Take the absolute value, or positive value, and divide by the actual steps.
Then multiply by 100 to get a percent. Here is the formula:
|Actual - Measured| ÷ Actual X 100
Record the percent accuracy of each device’s measurements, then calculate the
average percent accuracy of each device.
Device/App
Percent accuracy
average
Conclusion
Based on your calculations, we can form a conclusion of which device is most
precise and accurate. Put your conclusion in the form of a conclusion statement.
Discussion: What new questions do you have about the precision or accuracy of
step-tracker apps and devices?
Vocabulary Practice
Circle the correct terms:
Three different people weigh a standard mass of 4.00 g on the same balance.
Each person obtains a reading of exactly 5.66 g for the mass of the standard.
These results imply that the balance was (precise/imprecise) and
(accurate/inaccurate).
Theoretically, a reaction between one mole of sodium and one mole of chloride
should yield 42 grams of sodium chloride. In your experiment, repeated 3
times, you measured 41.9 g, 42.0 g, and 41.9 g. Your results were
(precise/imprecise) and (accurate/inaccurate).
Students measured a standard 1-cm cube. Their measurements were: 0.89 cm,
0.99 cm, 0.77 cm, 1.16 cm, 0.88 cm, 1.08 cm. These measurements are
(precise/imprecise) and (accurate/inaccurate).