# Doing Psychological Research: Gathering and Analysing Data

By Nicky Hayes | Go to book overview

18
Correlation and regression

Correlation
Regression
Multivariate analysis

In the last chapter, we looked at tests that we can use when we have two sets of data and want to compare them, to see if they are significantly different. In this chapter, we will be looking at tests which can look at two sets of data and estimate how similar they are – not in terms of their specific values, or the actual measuring scale which has been used to obtain them, but in terms of how they vary.

In the first part of this chapter we will be looking at this from two sides. We will begin by looking at correlation, which is concerned with expressing the numerical relationship between two variables. Then we will go on to look at regression, which is still about correlation in many ways, but looks at it from a slightly different angle. It is useful for us to look at regression as well as correlation, because once we understand both of them, we can use the two approaches – correlation and regression analysis – to help us to make sense of several variables at a time. This is what we will be looking at in the second part of the chapter, and it will begin our exploration of analysis of variance, which we will be continuing in Chapter 19.

Correlation

A correlation test is exactly what its name suggests – a test which looks for co-relations. If we say that two variables are correlated, what we mean is that they vary in similar ways – that a certain size of score on one variable is likely to be associated with a certain size of score on the other. It might mean that a large score on one variable is likely to be associated with a large score on the other. If so, that would be a positive correlation. Or it might mean that a large score on one variable is likely to be associated with a small score on the other. That would be a negative correlation.

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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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