Measurement in ScienceMaking our efforts worthwhile

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?

Using tools properly!

• What would you record for the length of the blue line? (ruler is in cm)

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!

Try it again

• The balance measures mass (g)

• 200+60+(front beam reading)

• What should it be?

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!

The target analogy

• Bullseye = our accepted value

• Have we been accurate?

• How about precise?

• In this case, have we been accurate?

• How about precise?

• Which would be more important? Why do you think so?

• Well which outcome below would you be most impressed with?

ALL bull's-eyes, ALL the time!• That should be the goal!