Question

Two students are working on an AP Chemistry lab. Their assignment is to determine experimentally the density of a nonvolatile organic liquid, limestone. The accepted value for the density of limestone is $0.8422g/mL$. Each student conducts three separate density determinations, then calculates a mean (average) value for the density and the standard deviation for their three trials.

	Student A	Student B
Density #$1$	$0.8421g/mL$	$0.8408g/mL$
Density #$2$	$0.8514g/mL$	$0.8502g/mL$
Density #$3$	$0.8355g/mL$	$0.8332g/mL$
Mean Density	$0.8430g/mL$	$0.8414g/mL$
Standard Deviation	$0.0080$	$0.0085$

The results and calculations for each students are shown in the table below.
Of the four descriptions given below, which BEST interprets the accuracy and precision of Student A and Student B?

• A. Student A and Student B are equally precise, but Student B has more accurate results.
• B. Student A and Student B are equally accurate, but Student B has more precise results.
• C. Student A and Student B have equal accuracy and equal precision.
• D. Student A has more accurate and more precise results than Student B.

Answer 1

The correct option is B Student A and Student B are equally accurate, but Student B has more precise results.

$\begin{array}{cc}\text{Accuracy}\to & \text{It measures the closeness between the observed or}\\ & \text{determined value and true value of a quantity.}\\ \text{Precision}\to & \text{It measures how close the values are from}\\ & \text{one another in multiple observations.}\end{array}$

$\begin{array}{c}\text{Thus, student}A\text{and}B\text{have equal accuracy but}\\ \text{student}B\text{has more precisions than}A\text{.}\\ \text{So, option (B) is correct.}\end{array}$