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Descriptive statistics

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If your dissertation or project involved the generation of data, you will have collected 'raw' data. You must put this data into a manageable form, and make sense of it for your readers. This is an important stage in the research process because before you can use your data to attempt to answer your research question, you must first present what you found.

The way you organize and describe your data will depend on the type of data you've collected. If you have conducted an open-ended questionnaire, you'll need to look for patterns and trends in the responses. If you have numerical data generated during an experiment, you will need to use statistics to summarise and display this data. You are probably aware of the three most commonly used descriptive statistics: mean, median and mode. They are used to describe the middle of a data set (the 'central tendency').

Warning! Descriptive statistics are used to group and describe your data, they cannot be used to explain or draw conclusions from the data - to do this you need to analyse your data.

All data is different, and finding the appropriate way to analyse your data can be tricky. If you are unsure about what you need to do, discuss it with your supervisor as they will be able to guide you.

If, like many of us, you go pale at the very mention of the word 'statistics', the next activity will provide a gentle introduction to some of the basics.

Activity: descriptive statistics: an introduction - 30 minutes

In this activity, we'll remind you of some of the commonly used tests you can use to describe your data. It's your job to find out which you'll need to use and how to use them.

You might find the Engage in research: Gentle Introduction to Statistics useful when completing this activity. Although it's aimed at bioscience students, it has useful information for students from any subject.

1. The three most common descriptive statistics used to describe the mid-point of a data set are...

  • mean
  • median
  • mode

2. For each of these, find out...

  • what it describes
  • how you would calculate it

3. Consider which of these you will need to use to describe your data. It's always a good idea to find an average value for your data, but you may not need to find the mean, median and the mode.

4. Next, you'll need to consider the variability of your data set: how much your data is spread. The three most common descriptive statistics used to describe the spread of a data set are...

  • range
  • variance
  • standard deviation

5. Again, for each of these, find out what it describes and how you would calculate it.

6. Consider which of these test(s) you will need to use to describe your data.

7. Finally, if in doubt, talk to your supervisor.

If you would like more information about descriptive statistics, or more practice using them, visit Engage in research: Gentle Introduction to Statistics and have a go at some of the activities.

Next we look at displaying data.

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