Accuracy, precision and percent error

Answer Key - Grade 10 Science Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   Three weighings of a cup of water give 25.2 g, 25.5 g and 25.3 g. What is the mean mass, to 0.01 g, Ari?

   25.33 g
2. 2.

   Three weighings of a jar of sand give 98.6 g, 99.1 g and 98.8 g. What is the mean mass, to 0.01 g, Esme?

   98.83 g

3. Read this first

   Three groups measure the density of table salt (CRC accepted value 2.17 g/cm³) (example data)

   group	trial 1	trial 2	trial 3
   Group 1	2.16	2.17	2.18
   Group 2	2.3	2.31	2.3
   Group 3	2.05	2.3	2.16

4. 3.

   Using the table, which group is both accurate and precise, Jun?

   • Group 2
   • Group 1
   • Group 3
5. 4.

   Using the table, how would you describe Group 2, Kira?

   • Precise, not accurate
   • Accurate and precise
   • Neither accurate nor precise
6. 5.

   Using the table, why isn't Group 3 precise, Luz?

   • Its trials spread widely
   • It did too many trials
   • Its mean is far from 2.17
7. 6.

   A balance reads 0.20 g with nothing on it. What happens to every mass measured, Milo?

   • They scatter at random
   • Each one reads 0.20 g too low
   • Each one reads 0.20 g too high
8. 7.

   Water in a cylinder is read from above, not at eye level. What error results, Noah?

   • The water evaporates
   • The reading is too high
   • The cylinder stretches a little
9. 8.

   Some water stays stuck inside a cylinder after pouring. What does that do to the poured volume, Pia?

   • More is poured than measured
   • Less is poured than measured
   • The water gets heavier
10. 9.

    How can a group make its results more reliable, Ren?

    • Round each number to the nearest whole number
    • Repeat the trials and average
    • Use just one trial
11. 10.

    Why zero a balance before weighing, Zee?

    • To warm it up
    • To remove a constant offset
    • To make it more sensitive