Measurement in Science Making our efforts worthwhile
Dec 25, 2015
Why Measure?• A key element of science is EXPERIMENTS
• When experimenting, our data is collected through MEASUREMENTS
• If the measurements are no good, why bother experimenting at all?
Estimating the last digit• When making measurements, you ALWAYS estimate the
last digit of the measurement.
• If the measurement of the volume of a container is halfway between 1 L and 2 L, you don’t round it! You write 1.5 L
• If it was barely over 1 L, say maybe 1/10 the way to 2 L, you write 1.1 L – ESTIMATE!
Graduated Cylinders
• Graduated cylinders measure volume.
• They have a specific issue however
• What is happening with the liquid?
• Where do we measure it?
• The curve is called the MENISCUS.
• Water is attracted to the sides of the cylinder and are pulled up.
• The TRUE value is at the BOTTOM of the mensicus
Accuracy and precision• Accuracy = your measurement is close to an accepted or
expected value
• Precision = each of your measurements are very close to all other measurements
• It is possible to be precise without being accurate, or to be accurate without being precise!
• In this case, have we been accurate?
• How about precise?
• Which would be more important? Why do you think so?