Question

Several groups of students are attempting to determine the density of a lead weight by various methods. Their data is shown in

the table. A handbook lists the density of lead as 11.3 g/mL.
Group 1
Group 2
Group 3
Measured density (g/mL), trial 1
11.5
11.5
10.9
Measured density (g/mL), trial 2
11.3
11.4
11.3
Measured density (g/mL), trial 3
11.1
11.4
11.1
Average density (g/mL)
11.3
11.4
11.1
Which group was most accurate?
Which group was most precise?
O Group 2
O Group 3
O Group 1
O Group 3
O Group 2
O Group 1

Answer 1

accurate: Group 1

precise: Group 2

Step-by-step explanation:

Accuracy is a measure of how close a measured value is to the true value. Here, we assume the handbook value (11.3) to be the true value. Group 1 arrived at this number, so must be considered to have made the most accurate measurement.

Answer 2

• accurate: Group 1
• precise: Group 2

Step-by-step explanation:

Accuracy is a measure of how close a measured value is to the true value. Here, we assume the handbook value (11.3) to be the true value. Group 1 arrived at this number, so must be considered to have made the most accurate measurement.

__

Usually, precision refers to the value of the least significant digit of the measurement. Here, all measurements were made to 3 significant digits, with the least digit being tenths. On that basis, no group can claim better precision than any other.

Another way to consider precision is to look at the variation in measured values. Group 2's values were the most consistent, having a range of 0.1 g/mL. Group 1's values had a range of 0.4 g/mL (from 11.1 to 11.5), and Group 3's values also ranged over 0.4 g/mL (from 10.9 to 11.3).

Because Group 2 had the most consistent readings, we award them the title of most precise.