How to Design and Report Experiments

399 Pages·2003·83.12 MB·English

by  Andy Field

How to Design and Report
'
Experiments

How to Design and Report
'
Experiments
Andy Field
Graham Hole
ISAGE
Los Angeles I London I New Delhi
Singapore I Washington DC
© 2003
First published 2003
Reprinted 2010, 20I I, 20I2, 2013
All rights reserved. No part of this publication may be reproduced,
stored in a retrieval system, transmitted or utilized in any form or by
any means, electronic, mechani'cal, photocopying, recording or
otherwise, without permissioh,in writing from the Publishers.
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British Library Cataloguing in Publication data
A catalogue record for this book is available from the British Library
ISBN 978 0 76I9 7382 9
ISBN 978 0 76I9 7383 6 (pbk)
Library of Congress Control Number: 2002108293
Typeset by Keyword Typesetting Services
Printed in Great Britain by Group
"
MIX
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Paper from
responslble sources
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Contents
Preface IX
Acknowledgements XI
Part 1: Designing an Experiment 1
1 Before You Begin 3
1.1 Variables and Measurement 5
1.2 Experimental versus Correlational Research 10
1.3 The Dynamic Nature of Scientific Method 27
1.4 Summary 29
1.5 Practical Tasks 29
1.6 Further Reading 32
2 Planning an Experiment 33
2.1 What Should I Research: Finding Out What's Been
Done? 33
2.2 How Do I Research My Question? 37
2.3 Summary: Is That It? 51
2.4 Practical Tasks 52
2.5 Further Reading 53
3 Experimental Designs 54
3.1 The Three Aims of Research: Reliability, Validity and
Importance 54
3.2 Different Methods for Doing Research 63
3.3 So, Which Experimental Design Should You Use? 96
3.4 Ethical Considerations in Running a Study 98
3.5 Summary 101
3.6 Practical Tasks 102
3.7 Further Reading 104
vi Contents
Part 2: Analysing and Interpreting Data 107
4 Descriptive Statistics 109
4.1 Populations and Samples 109
4.2 Summarizing Data 111
4.3 Confidence Intervals 135
4.4 Reporting Descriptive Statistics 136
4.5 Summary 139
4.6 Practical Tasks 140
4.7 Further Reading 140
5 Inferential Statistics 141
5.1 Testing Hypotheses 141
5.2 Summary 157
5.3 Practical Tasks 157
5.4 Further Reading 158
6 Parametric Statistics 159
6.1 How Do I Tell If My Data are Parametric? 159
6.2 The t-Test 162
6.3 The Independent t-Test 163
6.4 The Dependent t-Test 168
6.5 Analysis of Variance 172
6.6 One-Way Independent ANOVA 174
6.7 One-Way Repeated Measures ANOVA 183
6.8 Two Way Independent ANOVA 191
6.9 Two-Way Mixed ANOVA 201
6.10 Two-Way Repeated Measures ANOVA 212
6.11 Analysis of Covariance (ANCOVA) 223
6.12 Summary 231
6.13 Practical Tasks 231
6.14 Further Reading 232
7 Non-parametric Statistics 234
7.1 Non-Parametric Tests: Rationale 234
7.2 The Mann-Whitney Test 235
7.3 The Wilcoxon Signed-Rank Test 239
7.4 The Kruskal-Wallis Test 244
7.5 Friedman's ANOVA 250
7.6 Summary 256
7.7 Practical Tasks 256
7.8 Further Reading 256
8 Choosing a Statistical Test 258
8.1 The Need to Think About Statistics at the Outset of
Designing a Study 258
8.2 Five Questions to Ask Yourself 265
Contents vii
8.3 Specific Sources of Confusion in Deciding Which Test to
u~ 2~
8.4 Examples of Using These Questions to Arrive at the
Correct Test 271
8.5 Summary 277
8.6 · Practical Tasks 277
Part 3: Writing Up Your Research 285
9 A Quick Guide to Writing a Psychology Lab-Report 287
9.1 An Overview of the Various Sections of a Report 287
9.2 Title 289
9.3 Abstract 289
9.4 Introduction 289
9.5 Method 291
9.6 Results 293
9.7 Discussion 295
9.8 References 298
10 General Points When Writing a Report 301
10.1 The Standardized Format of the Report 301
10.2 Some Important Considerations When Writing a Report 303
10.3 Writing Style 304
10.4 Give Yourself Enough Time 307
10.5 Summary 308
10.6 Practical Tasks 309
10.7 Further Reading 309
11 Answering the Question 'Why?' The Introduction Section 311
11.1 Providing a Rationale 311
11.2 How to Describe Previous Research and its Findings 313
11.3 Outlining Your Own Experiment 315
11.4 Providing Predictions About the Experiment's Outcome 316
11.5 Summary 317
11.6 Practical Tasks 317
12 Answering the Question 'How?' The Method Section 320
12.l Design 320
12.2 Participants 321
12.3 Apparatus 322
12.4 Procedure 323
12.5 Summary 324
12.6 Practical Tasks 324
13 Answering the Question 'What Did I Find?' The Results Section 327
13.1 Tidying Up Your Data 327
13.2 Descriptive Statistics 328
viii Contents
13.3 Inferential Statistics 330
13.4 Make the Reader's Task Easy 332
13.5 Be Selective in Reporting Your Results! 333
13.6 Summary 333
14 Answering the Question 'So What'? The Discussion Section 336
14.1 Summarize Your Findings 336
14.2 Relate Your Findin,gs to Previous Research 336
14.3 Discuss the Limitations of Your Study 340
14.4 Make Suggestions for Further Research 341
14.5 Draw Some Conclusions 342
14.6 Summary 342
15 Title, Abstract, References and Formatting 343
15.1 The Title 343
15.2 The Abstract 344
15.3 References 345
15.4 Appendices 356
15.5 Practical Tasks 357
.16 Example of an Experimental Write-Up 360
16.1 Abstract 360
16.2 Introduction 361
16.3 Method 364
16.4 Design 364
16.5 Procedure 365
16.6 Results 366
16.7 Discussion 368
16.8 References for the Example 371
References 373
Index 379
Preface
A long time ago in a galaxy far, far away there lived a race of aliens
who had no difficulty with the finer points of experimental design. For
centuries the forces of the 'dark side' imposed a rigid regime of learn
ing and practising experimental design. The strain of writing lab
report after lab-report day in, day out, proved too much for some.
A small rebel alliance escaped from the planet in an old x-axis star
fighter. They found their way to an attractive small blue-green planet
called Earth where they inter-married with a set of hairy apes that
were scratching their heads about how to work out whether their
leader had significantly more bananas than them. We are their des
cendants. The rest is what we now call history, but this aversion to
designing and reporting experiments has stayed in our racial memory.
So, if you want to know whether your leader has significantly more
bananas than you, this is the book for you!
There are many worthy books on experimental design on the mar
ket, so why have we written another one? Well, few books take you
logically through the process of doing an experiment (from the stage
of having the initial idea right through to delivering the finished lab
report). Those that do probably don't have as many jokes in them as
this one (and they certainly don't have dogs and cats). Over the years
that we've both lectured on experimental design and statistics, we've
noticed that a bit of humour (well, we think it's humour at least) goes
a long way in helping to relieve the potential stress of the topic-for
the students and for us. So, this book isn't as big as it looks and
certainly not as scary!