Variation not only occurs between species but also between members of the same species. In order to get a better understanding of this scientists carry out investigations.

When carrying out investigations random sampling is very important. First of all it would be near impossible to sample the whole of a species. Therefore, on a practical level, a sample makes much more sense. However, it’s important that this sample is random to eliminate any systematic bias.

After the data has been collected there are a number of ways in which it can be understood. One way is to calculate the mean. This is basically the average of the data and can be calculated by adding all the data together and then dividing by the total number of results.

The normal distribution of the mean is important in statistical analysis. To work this out you take several sets of random samples and then calculate the mean for each one. Your answer, therefore, will refer not to the distribution of the population but the population mean. Each time you calculate the normal distribution and plot the points you should end up with a bell shaped curve.

Standard deviation also measures variation within a sample. This shows how spread out the data in a sample is and how close different points of data are to the mean of the sample. The closer to zero the answer is the closer all the values are to the mean. However, a bigger value would suggest that the data points are further from the value of the mean.

To find out more about investigating techniques go to the INVESTIGATIVE AND PRACTICAL SKILLS section.