0.2 B2, B3: Accuracy, Precision, And Units

A student observes a garden plot. Several plants shaded by a tree are not as large as those of the same species growing in the full sun. The student asks, “Why are the plants growing in the shade smaller than the plants growing in the sun?”  Which is the most reasonable hypothesis to explain the student’s observations?

• The tree removes water from the soil. The drier soil limits the growth of those plants growing near the tree.

• The tree removes minerals from the soil. The mineral-reduced soil limits the growth of those plants growing near the tree.

• The tree blocks sunlight, lowering the light level in the shaded area. This limits the growth of this plant species, which grows best in direct sunlight.

• Answer option 4

Which of the following will allow measurement of a liquid’s volume with the greatest precision? 

• 50 mL cylinder graduated in 1 mL increments

• 100 mL cylinder graduated in 0.5 mL increments

• 100 mL cylinder graduated in 1 mL increments

• 200 mL cylinder graduated in 5 mL increments

A student performed an analysis of a sample for its calcium content and got the following results: 14.92%    14.91%   14.88%  14.91%   The actual amount of calcium in the sample is 14.90%.  What conclusions can you draw about the accuracy and precision of these results?  

• While precise, these results are not accurate.

• While accurate, these results are not accurate.

• These results are both accurate and precise.

• These results are neither accurate nor precise.

A student needs to collect quantitative data about the pendulum lab. Which of the following is NOT considered quantitative data?

• Length of string

• Initial dropping height

• Period of the swing

• Material used to change mass

In our pendulum lab our hypotheses could have arisen from....

• Observations

• Prior Knowledge

• Inferences

• All of the above

Which tool below is most precise?  Trial Volume Shown by Graduated Cylinder Volume Shown by the Buret 1 25 mL 26.54 mL 2 25 mL 26.51 mL 3 25 mL 26.60 mL 4 25 mL 26.49 mL 5 25 mL 26.57 mL Average 25 mL 26.54 mL      

• Graduated Cylinder because it is closest to the actual answer

• Buret because it has the smallest increments.

• Graduated Cylinder because it rounds to a whole number

• Buret because it is closest to the actual answer.

In the pendulum lab, it was important that we began by....

• Making a hypothesis

• Making observations

• Checking precision of testing instruments

• Generating a testable question

To determine the volume of a cube, a student measured one of the sides of the cube several times.  If the true length of the side is 10.62cm, give an example of four sets of measurements that would illustrate the following.   a. imprecise and inaccurate data     

To determine the volume of a cube, a student measured one of the sides of the cube several times.  If the true length of the side is 10.62cm, give an example of four sets of measurements that would illustrate the following.   b. precise but inaccurate data       

To determine the volume of a cube, a student measured one of the sides of the cube several times.  If the true length of the side is 10.62cm, give an example of four sets of measurements that would illustrate the following.   c. precise and accurate data

Think back to the activity from class: Why is it important that scientists have a "common language" of measurement? Explain in 3-5 sentences, and include at least one example.