Adam Mackridge, Philip Rowe

A Practical Approach to Using Statistics in Health Research (eBook, ePUB)

From Planning to Reporting

• Format: ePub

Produktbeschreibung

A hands-on guide to using statistics in health research, from planning, through analysis, and on to reporting A Practical Approach to Using Statistics in Health Research offers an easy to use, step-by-step guide for using statistics in health research. The authors use their experience of statistics and health research to explain how statistics fit in to all stages of the research process. They explain how to determine necessary sample sizes, interpret whether there are statistically significant difference in outcomes between groups, and use measured effect sizes to decide whether any changes are large enough to be relevant to professional practice. The text walks you through how to identify the main outcome measure for your study and the factor which you think may influence that outcome and then determine what type of data will be used to record both of these. It then describes how this information is used to select the most appropriate methods to report and analyze your data. A step-by-step guide on how to use a range of common statistical procedures are then presented in separate chapters. To help you make sure that you are using statistics robustly, the authors also explore topics such as multiple testing and how to check whether measured data follows a normal distribution. Videos showing how to use computer packages to carry out all the various methods mentioned in the book are available on our companion web site. This book: Covers statistical aspects of all the stages of health research from planning to final reporting Explains how to report statistical planning, how analyses were performed, and the results and conclusion Puts the spotlight on consideration of clinical significance and not just statistical significance Explains the importance of reporting 95% confidence intervals for effect size Includes a systematic guide for selection of statistical tests and uses example data sets and videos to help you understand exactly how to use statistics Written as an introductory guide to statistics for healthcare professionals, students and lecturers in the fields of pharmacy, nursing, medicine, dentistry, physiotherapy, and occupational therapy, A Practical Approach to Using Statistics in Health Research:From Planning to Reporting is a handy reference that focuses on the application of statistical methods within the health research context.

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Produktdetails

• Verlag: John Wiley & Sons
• Seitenzahl: 240
• Erscheinungstermin: 6. April 2018
• Englisch
• ISBN-13: 9781119383611
• Artikelnr.: 57005931

Autorenporträt

Adam Mackridge, Ph.D., is a Research Pharmacist at Betsi Cadwaladr University Health Board in North Wales. He has over 15 years of experience in planning, conducting and reporting health research. He received his PhD in Pharmacy Practice from Aston University in Birmingham, UK. Philip Rowe, Ph.D., is a Visiting Research Fellow in the School of Pharmacy and Molecular Sciences at Liverpool John Moores University, Liverpool, UK. He is a Fellow of the Royal Statistical Society and has authored other statistically based books for Wiley.

Inhaltsangabe

About the Companion Website xv 1 Introduction 1 1.1 At Whom is This Book Aimed? 1 1.2 At What Scale of Project is This Book Aimed? 2 1.3 Why Might This Book be Useful for You? 2 1.4 How to Use This Book 3 1.5 Computer Based Statistics Packages 4 1.6 Relevant Videos etc. 5 2 Data Types 7 2.1 What Types of Data are There and Why Does it Matter? 7 2.2 Continuous Measured Data 7 2.2.1 Continuous Measured Data - Normal and Non
Normal Distribution 8 2.2.2 Transforming Non
Normal Data 13 2.3 Ordinal Data 13 2.4 Categorical Data 14 2.5 Ambiguous Cases 14 2.5.1 A Continuously Varying Measure that has been Divided into a Small Number of Ranges 14 2.5.2 Composite Scores with a Wide Range of Possible Values 15 2.6 Relevant Videos etc. 15 3 Presenting and Summarizing Data 17 3.1 Continuous Measured Data 17 3.1.1 Normally Distributed Data - Using the Mean and Standard Deviation 18 3.1.2 Data With Outliers, e.g. Skewed Data - Using Quartiles and the Median 18 3.1.3 Polymodal Data - Using the Modes 20 3.2 Ordinal Data 21 3.2.1 Ordinal Scales With a Narrow Range of Possible Values 22 3.2.2 Ordinal Scales With a Wide Range of Possible Values 22 3.2.3 Dividing an Ordinal Scale Into a Small Number of Ranges (e.g. Satisfactory/Unsatisfactory or Poor/Acceptable/Good) 22 3.2.4 Summary for Ordinal Data 23 3.3 Categorical Data 23 3.4 Relevant Videos etc. 24 Appendix 1: An Example of the Insensitivity of the Median When Used to Describe Data from an Ordinal Scale With a Narrow Range of Possible Values 25 4 Choosing a Statistical Test 27 4.1 Identify the Factor and Outcome 27 4.2 Identify the Type of Data Used to Record the Relevant Factor 29 4.3 Statistical Methods Where the Factor is Categorical 30 4.3.1 Identify the Type of Data Used to Record the Outcome 30 4.3.2 Is Continuous Measured Outcome Data Normally Distributed or Can It Be Transformed to Normality? 30 4.3.3 Identify Whether Your Sets of Outcome Data Are Related or Independent 31 4.3.4 For the Factor, How Many Levels Are Being Studied? 32 4.3.5 Determine the Appropriate Statistical Method for Studies with a Categorical Factor 32 4.4 Correlation and Regression with a Measured Factor 34 4.4.1 What Type of Data Was Used to Record Your Factor and Outcome? 34 4.4.2 When Both the Factor and the Outcome Consist of Continuous Measured Values, Select Between Pearson and Spearman Correlation 34 4.5 Relevant Additional Material 38 5 Multiple Testing 39 5.1 What Is Multiple Testing and Why Does It Matter? 39 5.2 What Can We Do to Avoid an Excessive Risk of False Positives? 40 5.2.1 Use of Omnibus Tests 40 5.2.2 Distinguishing Between Primary and Secondary/ Exploratory Analyses 40 5.2.3 Bonferroni Correction 41 6 Common Issues and Pitfalls 43 6.1 Determining Equality of Standard Deviations 43 6.2 How Do I Know, in Advance, How Large My SD Will Be? 43 6.3 One
Sided Versus TwöSided Testing 44 6.4 Pitfalls That Make Data Look More Meaningful Than It Really Is 45 6.4.1 Too Many Decimal Places 45 6.4.2 Percentages with Small Sample Sizes 47 6.5 Discussion of Statistically Significant Results 47 6.6 Discussion of Non
Significant Results 50 6.7 Describing Effect Sizes with Non
Parametric Tests 51 6.8 Confusing Association with a Cause and Effect Relationship 52 7 Contingency Chi
Square Test 55 7.1 When Is the Test Appropriate? 55 7.2 An Example 55 7.3 Presenting the Data 57 7.3.1 Contingency Tables 57 7.3.2 Clustered or Stacked Bar Charts 57 7.4 Data Requirements 59 7.5 An Outline of the Test 59 7.6 Planning Sample Sizes 59 7.7 Carrying Out the Test 60 7.8 Special Issues 61 7.8.1 Yates Correction 61 7.8.2 Low Expected Frequencies - Fisher's Exact Test 61 7.9 Describing the Effect Size 61 7.9.1 Absolute Risk Difference (ARD) 62 7.9.2 Number Needed to Treat (NNT) 63 7.9.3 Risk Ratio (RR) 63 7.9.4 Odds Ratio (OR) 64 7.9.5 Case: Control Studies 65 7.10 How to Report the Analysis 65 7.10.1 Methods 65 7.10.2 Results 66 7.10.3 Discussion 67 7.11 Confounding and Logistic Regression 67 7.11.1 Reporting the Detection of Confounding 68 7.12 Larger Tables 69 7.12.1 Collapsing Tables 69 7 12.2 Reducing Tables 70 7.13 Relevant Videos etc. 71 8 Independent Samples (TwöSample) T
Test 73 8.1 When Is the Test Applied? 73 8.2 An Example 73 8.3 Presenting the Data 75 8.3.1 Numerically 75 8.3.2 Graphically 75 8.4 Data Requirements 75 8.4.1 Variables Required 75 8.4.2 Normal Distribution of the Outcome Variable Within the Two Samples 75 8.4.3 Equal Standard Deviations 78 8.4.4 Equal Sample Sizes 78 8.5 An Outline of the Test 78 8.6 Planning Sample Sizes 79 8.7 Carrying Out the Test 79 8.8 Describing the Effect Size 79 8.9 How to Describe the Test, the Statistical and Practical Significance of Your Findings in Your Report 80 8.9.1 Methods Section 80 8.9.2 Results Section 80 8.9.3 Discussion Section 81 8.10 Relevant Videos etc. 81 9 Mann-Whitney Test 83 9.1 When Is the Test Applied? 83 9.2 An Example 83 9.3 Presenting the Data 85 9.3.1 Numerically 85 9.3.2 Graphically 85 9.3.3 Divide the Outcomes into Low and High Ranges 85 9.4 Data Requirements 86 9.4.1 Variables Required 86 9.4.2 Normal Distributions and Equality of Standard Deviations 87 9.4.3 Equal Sample Sizes 87 9.5 An Outline of the Test 87 9.6 Statistical Significance 87 9.7 Planning Sample Sizes 87 9.8 Carrying Out the Test 88 9.9 Describing the Effect Size 88 9.10 How to Report the Test 89 9.10.1 Methods Section 89 9.10.2 Results Section 89 9.10.3 Discussion Section 90 9.11 Relevant Videos etc. 91 10 One
Way Analysis of Variance (ANOVA) - Including Dunnett's and Tukey's Follow Up Tests 93 10.1 When Is the Test Applied? 93 10.2 An Example 93 10.3 Presenting the Data 94 10.3.1 Numerically 94 10.3.2 Graphically 94 10.4 Data Requirements 94 10.4.1 Variables Required 94 10.4.2 Normality of Distribution for the Outcome Variable Within the Three Samples 95 10.4.3 Standard Deviations 96 10.4.4 Sample Sizes 98 10.5 An Outline of the Test 98 10.6 Follow Up Tests 98 10.7 Planning Sample Sizes 99 10.8 Carrying Out the Test 100 10.9 Describing the Effect Size 101 10.10 How to Report the Test 101 10.10.1 Methods 101 10.10.2 Results Section 102 10.10.3 Discussion Section 102 10.11 Relevant Videos etc. 103 11 Kruskal-Wallis 105 11.1 When Is the Test Applied? 105 11.2 An Example 105 11.3 Presenting the Data 106 11.3.1 Numerically 106 11.3.2 Graphically 107 11.4 Data Requirements 109 11.4.1 Variables Required 109 11.4.2 Normal Distributions and Standard Deviations 109 11.4.3 Equal Sample Sizes 110 11.5 An Outline of the Test 110 11.6 Planning Sample Sizes 110 11.7 Carrying Out the Test 110 11.8 Describing the Effect Size 111 11.9 Determining Which Group Differs from Which Other 111 11.10 How to Report the Test 111 11.10.1 Methods Section 111 11.10.2 Results Section 112 11.10.3 Discussion Section 113 11.11 Relevant Videos etc. 114 12 McNemar's Test 115 12.1 When Is the Test Applied? 115 12.2 An Example 115 12.3 Presenting the Data 116 12.4 Data Requirements 116 12.5 An Outline of the Test 118 12.6 Planning Sample Sizes 118 12.7 Carrying Out the Test 119 12.8 Describing the Effect Size 119 12.9 How to Report the Test 119 12.9.1 Methods Section 119 12.9.2 Results Section 120 12.9.3 Discussion Section 120 12.10 Relevant Videos etc. 121 13 Paired T
Test 123 13.1 When Is the Test Applied? 123 13.2 An Example 125 13.3 Presenting the Data 125 13.3.1 Numerically 125 13.3.2 Graphically 125 13.4 Data Requirements 126 13.4.1 Variables Required 126 13.4.2 Normal Distribution of the Outcome Data 126 13.4.3 Equal Standard Deviations 128 13.4.4 Equal Sample Sizes 128 13.5 An Outline of the Test 128 13.6 Planning Sample Sizes 129 13.7 Carrying Out the Test 129 13.8 Describing the Effect Size 129 13.9 How to Report the Test 130 13.9.1 Methods Section 130 13.9.2 Results Section 130 13.9.3 Discussion Section 131 13.10 Relevant Videos etc. 131 14 Wilcoxon Signed Rank Test 133 14.1 When Is the Test Applied? 133 14.2 An Example 134 14.3 Presenting the Data 134 14.3.1 Numerically 134 14.3.2 Graphically 136 14.4 Data Requirements 136 14.4.1 Variables Required 136 14.4.2 Normal Distributions and Equal Standard Deviations 137 14.4.3 Equal Sample Sizes 137 14.5 An Outline of the Test 137 14.6 Planning Sample Sizes 138 14.7 Carrying Out the Test 139 14.8 Describing the Effect Size 139 14.9 How to Report the Test 140 14.9.1 Methods Section 140 14.9.2 Results Section 140 14.9.3 Discussion Section 141 14.10 Relevant Videos etc. 141 15 Repeated Measures Analysis of Variance 143 15.1 When Is the Test Applied? 143 15.2 An Example 144 15.3 Presenting the Data 144 15.3.1 Numerical Presentation of the Data 145 15.3.2 Graphical Presentation of the Data 145 15.4 Data Requirements 146 15.4.1 Variables Required 146 15.4.2 Normal Distribution of the Outcome Data 148 15.4.3 Equal Standard Deviations 148 15.4.4 Equal Sample Sizes 148 15.5 An Outline of the Test 148 15.6 Planning Sample Sizes 149 15.7 Carrying Out the Test 150 15.8 Describing the Effect Size 150 15.9 How to Report the Test 151 15.9.1 Methods Section 151 15.9.2 Results Section 151 15.9.3 Discussion Section 152 15.10 Relevant Videos etc. 153 16 Friedman Test 155 16.1 When Is the Test Applied? 155 16.2 An Example 157 16.3 Presenting the Data 157 16.3.1 Bar Charts of the Outcomes at Various Stages 157 16.3.2 Summarizing the Data via Medians or Means 157 16.3.3 Splitting the Data at Some Critical Point in the Scale 159 16.4 Data Requirements 160 16.4.1 Variables Required 160 16.4.2 Normal Distribution and Standard Deviations in the Outcome Data 160 16.4.3 Equal Sample Sizes 160 16.5 An Outline of the Test 160 16.6 Planning Sample Sizes 161 16.7 Follow Up Tests 161 16.8 Carrying Out the Tests 162 16.9 Describing the Effect Size 162 16.9.1 Median or Mean Values Among the Individual Changes 162 16.9.2 Split the Scale 162 16.10 How to Report the Test 162 16.10.1 Methods Section 162 16.10.2 Results Section 163 16.10.3 Discussion Section 164 16.11 Relevant Videos etc. 164 17 Pearson Correlation 165 17.1 Presenting the Data 165 17.2 Correlation Coefficient and Statistical Significance 166 17.3 Planning Sample Sizes 167 17.4 Effect Size and Practical Relevance 167 17.5 Regression 169 17.6 How to Report the Analysis 170 17.6.1 Methods 170 17.6.2 Results 170 17.6.3 Discussion 171 17.7 Relevant Videos etc. 171 18 Spearman Correlation 173 18.1 Presenting the Data 173 18.2 Testing for Evidence of Inappropriate Distributions 174 18.3 Rho and Statistical Significance 174 18.4 An Outline of the Significance Test 175 18.5 Planning Sample Sizes 175 18.6 Effect Size 176 18.7 Where Both Measures Are Ordinal 176 18.7.1 Educational Level and Willingness to Undertake Internet Research - An Example Where Both Measures Are Ordinal 176 18.7.2 Presenting the Data 177 18.7.3 Rho and Statistical Significance 177 18.7.4 Effect Size 178 18.8 How to Report Spearman Correlation Analyses 178 18.8.1 Methods 178 18.8.2 Results 179 18.8.3 Discussion 180 18.9 Relevant Videos etc. 180 19 Logistic Regression 181 19.1 Use of Logistic Regression with Categorical Outcomes 181 19.2 An Outline of the Significance Test 182 19.3 Planning Sample Sizes 182 19.4 Results of the Analysis 184 19.5 Describing the Effect Size 184 19.6 How to Report the Analysis 185 19.6.1 Methods 185 19.6.2 Results 186 19.6.3 Discussion 186 19.7 Relevant Videos etc. 187 20 Cronbach's Alpha 189 20.1 Appropriate Situations for the Use of Cronbach's Alpha 189 20.2 Inappropriate Uses of Alpha 190 20.3 Interpretation 190 20.4 Reverse Scoring 191 20.5 An Example 191 20.6 Performing and Interpreting the Analysis 192 20.7 How to Report Cronbach's Alpha Analyses 193 20.7.1 Methods Section 193 20.7.2 Results 194 20.7.3 Discussion 194 20.7 Relevant Videos etc. 195 Glossary 197 Videos 209 Index 211