A table is a good way to organise your raw data. However, it can still be difficult to see any patterns in it. There are a number of ways in which you can analyse you data.

Mean: this is the average of your data. To find this you need to add all the data together and then divide by the number of values. However, this is not suitable if you have extreme values.

Standard deviation: this is a measurement of spread about the mean. The lower the standard deviation, the closer the data is around the mean. It can be good for comparing two different sets of results.

You use the following equation:

In order to calculate it you need to:

• calculate the difference between the actual value and the means by subtracting the mean from each of your values
• you then square each of these answers and add them together
• you then divide this answer by the number of values in your data set
• finally, square root this answer

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A2 STUDENTS

You’ll also be expected to know how to calculate:

• standard error and 95% confidence limits
• X²
• Spearman rank correlation