# Comparing results using percentage change

## In a nutshell

Being able to compare and analyse raw sets of data is a skill and there are a number of ways to do this depending on the specific point you may be trying to make.

### Equations

The percentage change equation calculates the difference in percentage.

$Percentage \ change =\frac {measured \ value - actual \ value}{actual \ value} \times 100$

## Percentage change

In a situation where you want to compare two results but they have different starting points, percentage change is a good way to compare them.

Commonly, means of data, as well as its range, will be used to compare results.

### Percentage change to actual value

When carrying out an experiment to obtain a scientific constant such as the acceleration of gravity or the molar gas constant, the following equation can be used.

$Percentage \ change =\frac {measured \ value - actual \ value}{actual \ value} \times 100$

Where the measured value is your experimental result and the actual value is the scientifically accepted value.

**Note: **It is important that the two aren't switched as percentage change can be negative.

- A
**positive** percentage change means the experimental value is **above** the actual value. - A
**negative** percentage change means the experimental value is **below** the actual value.

### Percentage change in a variable

When conducting experiments, a factor may change the measurements being collected. The percentage increase or decrease can be calculated using this equation:

$Percentage \ change = \frac {second \ measurement - first \ measurement}{first \ measurement} \times 100$

- A
**positive** percentage change means that the change of factor has caused the measurement to **increase**. - A
**negative** percentage change means that the change of factor has caused the measurement to **decrease**.