3.2.0 Measurements and Errors

What are SI units?

international system of units for all scientists to use the same units

Peta?

10^15

Tera?

10^12

Giga?

10^9

Mega?

10^6

Kilo?

10^3

Deci?

10^-1

Milli?

10^-3

Micro?

10^-6

Nano?

10^-9

Pico?

10^-12

Femto?

10^-15

Positive powers have capital or lowercase prefixes?

Capital

Negative powers have capital or lowercase prefix?

Lower case

What to give your answer to in terms sfg?

The same number as the number with the least number of sfg

Are error and mistake the same?

NO

What is an error?

Problems that arise beyond the control of the user or the programmer instead by the computer or machine

Can you repeat errors?

no you will still get it wrong

What is a true value?

This is the value that would be obtained in an ideal measurement.

What is measurement error?

The difference between what you measured...and what the real or "true" measure of the variable is. The amount of error in any measure varies. There could be considerable error in one measurement and very little in the next. Measurement error exists in both direct measures (like blood pressure) and indirect measures (like pain).

What does repeatable mean?

Same results can be obtained with same method and equipment

What does reproducible mean?

You can get the same results with a different method and equipment

What is uncertainty?

Interval where true value lies

What is resolution?

Smallest change in measured quantity an instrument can show

What are the basic units?

Length
Time
Substance
Current
Temperature
Mass
Luminous Intensity

What is the base unit for mass?

kilogram

base unit for length?

meter (m)

Base unit of time?

second (s)

Base unit of luminous intensity?

candela (cd)

Base unit of temperature?

Kelvin (K)

Base unit of electric current?

ampere, A

Base unit for substance amount?

moles (mol)

Two types of errors?

Random and Systematic

What are systematic errors?

Repeat measurements being consistently too high or low, possibly the result of an incorrectly zeroed balance, making all repeats incorrect by the same amount. So there is a constant deviation from true value

Example of systematic error?

Zero error
Incorrectly calibrated instruments
Mistiming an event

What is a random error?

Scatter of readings around a mean value

Reasons of random error?

Flawed observation
Insufficient precision

How to calculate uncertainty for a single data?

0.5 * the smallest increment

How to calculate the absolute uncertainty of a data set?

0.5 * the range

% uncertainty in diameter =

(absolute uncertainty / mean value) * 100

How to reduce systematic error?

Calibration curve and re-calibrating instrument

How to reduce random error?

Cannot be eliminated
Reduced by averaging out

What is the human reaction time?

0.2 to 0.25 seconds

What is precision?

a measure of how close a series of measurements are to one another

What is accuracy?

how close a measurement is to the true value

What is an error bar?

Graphical representation of the variability of data

How to calculate % uncertainty?

(Absolute / True Value)*100

When two values or added what to do to uncertainty?

Add the absolute uncertainty

When multiplied or divided how to find uncertainty?

Add the % uncertainty

When raised to the power how to find uncertainties?

Multiply the % uncertainty by the power

How to use a micrometer?

Look a folder diagram

How to use vernier caliper?

Use folder diagram

What are worst lines?

Lines of best fit which have the maximum and minimum possible slopes for the data which should go through all the error bars

What is the uncertainty in the gradient?

The difference between the best gradient and the worst gradient

What is the uncertainty in the y intercept?

Difference between best y intercept and worst y intercept

What are the prefixes?

Scaling factors