Uncertainties and Error in Experimental Measurement

Resources: Study Guide       

Key topics to know:

1. Random and Systematic

2. Accurate and Precise

3. Estimating Uncertainty

        a) From measuring device ... Analogue or Digital

        b) From several repeated measurements

4. Plotting Graphs

5. Handling Uncertainties in calculations

6. Error bars

Sample Problems

2. You measured the diameter of several glasses and had the following results: 7.4 cm, 7.6 cm, 8.1 cm, 7.7 cm, 7.8 cm, and 7.5 cm. What would you state as the diameter of this type of glass? What are the uncertainties?

3.  For the table to the right:

        a. Plot the points. Try to use as much of the coordinate plane (graph paper) as possible.

        b. Draw the error bars (vertical and horizontal)

        c. Draw line of best fit

        d. Draw maximum and minimum gradient lines

        e.  Calculate the slope of the line of best fit, max and min gradient lines.

 
Current. amps (A). plus or minus 0.05A Voltage. volts(V). plus or minus 0.25V
1.6 5.0
1.3 4.5
0.9 3.5
0.6 3.0
2.0 6.0

 

4. For the tables to the right (one with Excel and one by hand)

a. Plot the points. Try to use as much of the coordinate plane (graph paper) as possible.  Be sure to label the axes and title the graph.

b. Draw the error bars (vertical and horizontal)

c. Draw line of best fit.

d. Draw maximum and minimum gradient lines.

e.  Calculate the slope of the line of best fit, max and min gradient lines.  Show your work and include units in the solution.

f. Find the uncertainty of the gradient.

 

 
Force

F / N

+ or - 2 N

 Acceleration

a / m/s2

+ or - 0.2 m/s2
10 2.0
20 3.8
30 6.1
40 7.9
50 10.2

Time / seconds

+/- 0.5 s

Temperature / celcius

+/- 0.2 celcius

0
0.4
5
1.5
10
3.4
15
5.5
20
7.7
25
9.7
30
11.7
35
13.5
40
15.4