A measurement is only as good as the measuring device used. For example, a dollar bill is about 6 inches long. I could use this to measure the line and probably obtain a value within 2 inches of the correct length. However, if I used a ruler that is marked to each 1/8 of an inch, I could measure within 1/16 of an inch of the correct length. The uncertainty in a measurement is in the last digit of the measurement. It represents how much you had to estimate that last digit when making your measurement. a. When measuring the line above with the ruler on the back cover, which digits of your measurement would you be completely certain about? Which digits would you be less certain about? b. What is the largest amount by which you think the uncertain digits are incorrect? This is the uncertainty in your measurement.