Accuracy and Precision

Accurate and Precise

General Science 2 minutes read

Step into the shoes of an explorer mapping out unknown lands, just like the great explorers of the 15th and 16th centuries – think of Vasco da Gama or Christopher Columbus. Every step they took needed careful measurement; too short or too long, and their maps could lead ships astray.

In science, we use two important ideas when measuring: accuracy and precision. Accuracy tells us how close a measurement is to the true value, while precision shows how close repeated measurements are to each other.

In this activity, you’ll test three different scales – one without markings, one perfectly marked, and one incorrectly marked – to see which ones help you be accurate and precise, just like a skilled explorer navigating the seas.

Activity

Requirements

Notebook, book to measure, scale without markings, perfectly marked scale, incorrectly marked scale.

Procedure

  1. Take the scale without markings. Choose a book to measure and estimate its length using the scale. Write your measurement in your notebook.

  2. Each member of your group should repeat the process secretly, without sharing results.

  3. Take the one of the marked scales. Measure the same book carefully and record your measurement in your notebook. Keep it secret until everyone is done.

  4. Take the other marked scale. Measure the same book and record your measurement in your notebook, again keeping it secret.

  5. Once all measurements are recorded, use a trusted reference (e.g., a teacher-verified scale or the official measurement from a ruler) to find the true length of the book. Record this value.

  6. Compare the measurements from the three scales:

    1. Which ones are closest to the true length of the book? (accuracy)

    2. Which ones are very close to each other, even if they aren’t exactly correct? (precision)

  7. Discuss and identify which scale was perfect, which was incorrectly marked, and which lacked markings, based on the results.

Observations

Sr. No.

Length
(scale without markings)

Length
(first marked scale)

Length
(second marked scale)
1.      
2.      
3.      

Reflect and Discuss

  1. Which scale gave both accurate and precise measurements?

  2. Which scale gave precise but inaccurate measurements?

  3. Which scale was neither precise nor accurate?

  4. Which of the following is both precise and accurate?

    accuracy vs precisionEgon Willighagen, CC0, via Wikimedia Commons