Lecture: Measurement

English system: Metric system:

Resolution:

Smallest interval a tool can measure: how fine/close: # of decimal places: resolutions of your tv?

Accurate:

How close a measurement is to the true value: bulls-eye, cup/hole in golf?

Precision:

how close together repeated measurements are: arrows could be way off for accuracy but all grouped together; what could cause this?

When measuring you must ALWAYS determine what the resolution of the scale is.

For the following scales, determine the resolution first, then measure for accuracy where the arrow points;

Remember: no units = no credit

What is the measurement of the ruler at the arrow?

Resolution?

Accuracy?

Units?

What is the measurement at the arrow?

Resolution?

Accuracy?

Units?

How precise can this cm ruler be?What is the arrow measurement?

Resolution?Accuracy?Units?

Where is the arrow positioned?

Resolution?

Accuracy?

Units?

Reading a graduated cylinder: always at the bottom of the meniscus

How much liquid is in this graduated cylinder?

Resolution?

Accuracy?

Units?

What is the volume in this graduated cylinder?

Resolution?

Accuracy?

Units?

What is the volume in this graduated cylinder?

Resolution?

Accuracy?

Units?

Read the volume in the graduated cylinder

Resolution?

Accuracy?

Units?

What is the correct volume in the beaker?

Resolution?

Accuracy?

Units?

Rounding Rules• Accuracy also depends on rounding• Your calculator will often give you a number

indicating a greater degree of accuracy than possible (yes calculators can be wrong) so…– You must round– When a # is > to 5, round up:

resolution to the tenth: 3.76 3.8– When a # is < 5, round down:

resolution to the tenth: 5.14 5.1