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.