Honors Chemistry
Error/Percent Error Practice Problems
Name ___________________________ Pd ____ 9-23-13
4. A weather service office recorded the temperature at 4 field weather stations for three days and
compared it to the official temperature at the weather service office. What was the overall percent error of
the reported temperatures compared to the official temperature at the weather office.
Day
Official
Site
Field
Site 1
Field
Site 2
Field
Site 3
1
76.5
75.9
76.6
76.4
2
76.1
75.8
76.4
76.2
3
77.2
76.5
77.1
77.6
WHAT IS OUR STRATEGY HERE?
A.
B.
C.
D.
Calculate the AVERAGE temperature for EACH SITE across three days.
Calculate the ERROR for each site compared to the official site.
Calculate the AVERAGE ERROR for all the sites together.
Calculate the PERCENT ERROR comparing all sites to the official site.
A. Average Temperature for Official Site =
Average Temperature for Site 1 =
76.5 + 76.1 + 77.2 = 229.8 = 76.6
3
3
75.9 + 75.8 + 76.5 = 228.2 = 76.6
3
3
Average Temperature for Site 2 = 76.6 + 76.4 + 77.1 = 230.1 = 76.7
3
3
Average Temperature for Site 3 = 76.4 + 76.2 + 77.6
3
B. Error Site 1 = 76.6 - 76.6 = 0.0
Error Site 2 = 76.6 - 76.7 = -0.1
Error Site 3 = 76.7 – 76.6 = -0.1
= 230.2 = 76.7
C. Average Error =
_____0.0_
+
-0.1
+ ___-0.1_______ =
-0.07
3
D. Percent Error =
0.07
76.6
x 100 = 0.09% error
1. In lab, a group of 5 students each were asked to measure the mass of a small block of metal using a
triple beam balance. Each student recorded their measurement and retuned to their seat. Once all
students has found the block’s mass, the created a data table with their experimental measurements:
Student
1
2
3
4
5
Mass of block in grams
44.22
44.13
44.30
44.26
44.41
Once the data was recorded, the teacher revealed the accepted value of 44.29 g.
A. Overall, what percent error did the student measurements exhibit?
Average = 44.22+44.13+44.30+44.26+44.41 / 5 = 44.26
Error = 44.26 - 44.29 = -0.03
Percent Error =
0.03 x
44.29
100 = 0.07% error
B. Which student’s measurement had the least error? #3 The greatest error? #5
C. How could the student improve their overall results? Repeat measurements. Use a digital scale rather
than a triple beam. Read scale carefully…..