# Doing Psychological Research: Gathering and Analysing Data

By Nicky Hayes | Go to book overview

15
Numbers as descriptive
statistics

Measures of central tendency
Measures of dispersion
z scores
Summary tables
Content analysis

When we undertake research which provides us with quantitative data, those data come to us as lists of numbers. We obtain numbers, or scores, each time one of the participants in our study completes a task we have asked them to do; and since quantitative studies usually involve quite a lot of participants, those numbers come to us as long lists. But long lists of numbers are not easy for anyone to understand. So the first analytical task that we have to carry out on our data is to convert those lists of numbers into a form which allows us to see – and to grasp – what we have found more easily. This is the purpose of descriptive statistics.

Descriptive statistics, as we saw in the last chapter, are statistics which allow us to describe our data. They don't draw conclusions about probability, or allow us to infer how typical those scores may be. Instead, they give us an image of the data, allowing us to collect our information and present it clearly. Sometimes that image takes the form of more numbers – ones which summarise the information that we have found. But sometimes descriptive statistics take the form of graphic images, showing in pictures what the data are like. We will look at numerical descriptive statistics in this chapter, and graphical descriptive statistics in the next.

Numerical descriptive statistics, then, are ways of summarising research findings by using numbers. There are three main types of numerical descriptive statistics. The first ones we will look at are known as measures of central tendency. These are single numbers which are typical of, or represent, the data that we have obtained. The second

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Doing Psychological Research: Gathering and Analysing Data

• Title Page iii
• Contents vii
• List of Figures ix
• List of Tables xi
• List of Worked Examples xiii
• List of Formulae xiv
• Introduction xv
• Acknowledgements xix
• 1: Approaches to Psychological Research 1
• Part I - Gathering Data 15
• 2: Gathering Data for Psychological Research 17
• 3: Experiments 35
• 4: Observational Studies 55
• 5: questionnaire Studies 70
• 6: Psychometrics 91
• 7: Interviews 113
• 8: Case Studies and Ethnography 131
• 9: Analysing Documents 147
• Part II - Making Sense of Data 165
• 10: Introducing Qualitative Analysis 167
• 11: Grounded Approaches to Qualitative Research 183
• 12: Conversations, Discourse and Images 201
• 13: Protocol Analysis and Other Techniques 220
• 14: Introducing Quantitative Analysis 239
• 15: Numbers as Descriptive Statistics 257
• 16: Descriptive Statistics in Visual Images 278
• 17: Two-Sample Tests 303
• 18: Correlation and Regression 331
• 19: Analysis of Variance 349
• Glossary 366
• Statistical Tables 379
• References 387
• Index 392
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