Measuements and uncertainty.

This the independent variable?

The variable that is change by the researcher.

What is the dependant variable?

The variable that we are measuring.

The is the control variable?

Any variable that we keep constant throughout the experiment.

What is a random error?

Errors where measurements vary unpredictably.

What can cause random errors?

Factors that are not controlled in the experiment.

What are systematic errors?

Errors in which the measurements differ from the true by a consistent amount each time.

What can cause systematic errors?

The way in which measurements are taken.

Faulty measuring devices.

What is a zero error?

An error in which the reading is not zero when the quantity being measured is zero.

What can cause a zero error?

Fault measuring devices.

Measuring devices that haven’t been calibrated correctly.

Define accuracy.

How close a measurement is to the true value.

Define precision.

How close repeated measurements are to each other.

How do you express absolute uncertainty?

+- value.

How do you calculate percentage for uncertainty.

% uncertainty = absolute uncertainty/value x100

What is the resolution of an instrument?

The smallest detectable increment that can be measured.

What is the absolute uncertainty relative to resolution of an instrument.

Half the resolution.

When you add or subtract quantities from each other, what happens to the absolute uncertainty?

Add the absolute uncertainties together.

When you multiply or divide quantities, what happens to the percentage uncertainty?

Add the percentage uncertainties together.

When you raise a quantity to the power of n, what happens to the percentage uncertainty?

Multiply the percentage uncertainty by n.

What is the line of worst fit?

The least acceptable straight line through the data points.

This can either be the straightest or shallowest line.

What is the absolute uncertainty of the gradient of a line of best fit?

Difference between the gradient of the line of best fit and the line of worst fit.

How do you calculate the percentage uncertainty of a graph?

% uncertainty of graph = absolute uncertainty/gradient of line of best fit x100