Under the new GCSE specifications in Wales, practical work in Science will be examined. This unit will help students to prepare for the practical examination.

In this part of the paper, you will have to analyse your data and suggest or confirm a relationship between the independent variable (A), and the dependent variable (B). Here are some examples of relationships from graphs.

**No correlation** between variables A and B.

Variable A changes, B doesn’t change.

Variable B is independent of variable A.

**Direct proportion** between A and B.

A changes, B changes in the same ratio, eg if A doubles, so does B.

A graph that shows direct proportion is a straight rising line that goes through the origin.

An example of this might be if A is the resultant force on a dynamics trolley and B is the acceleration of the trolley. The acceleration of the trolley is directly proportional to the resultant force.

A and B are **proportional** to each other.

Variable A changes by a regular amount and so does B.

The graph does not go through the origin.

An example of this might be if A is a weight added to a spring and B is the length of the spring. The length of the spring is proportional to the weight added to it.

There is an **increasing positive correlation** between variables A and B.

A increases by a regular amount.

B increases at an increasing rate.

There is a **decreasing positive correlation** between variables A and B.

A increases by a regular amount.

B increases at a decreasing rate.

Variables A and B show **negative correlation** to each other.

A increases by a regular amount.

B decreases by a regular amount.

Variables A and B are **inversely proportional** to each other.

As A increases, B decreases.

As A doubles, B halves.

An example of this might be if A was the mass of a dynamics trolley and B was its acceleration. The acceleration of the trolley is inversely proportional to the mass of the trolley.