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INTRODUCTION

QUESTIONS TO CONSIDER

  1. What are the differences between descriptive statistics and inferential statistics?

  2. How do you determine if the results of a research study are clinically important?

  3. The median income in the United States is $44,000, but the mean income is $60,500. Why are these values different? Which value is likely to best describe incomes in the United States?

  4. Why is 0.05 typically chosen as the alpha value in a research study?

  5. Which value represents the difference between two treatments in a randomized clinical trial: alpha level, p-value, effect size, or number needed to treat?

CHAPTER-AT-A-GLANCE

This chapter will help you understand the following:

  • Interpretation of the results of an intervention research study

  • Reliability of measures used in rehabilitation studies

  • Reasons to use statistics to describe study results

  • Types of statistics: descriptive, inferential, clinically relevant

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Reading and interpreting study results can be challenging. If you develop a systematic approach, it becomes easier and faster to interpret the study findings. Chapters 3 and 4 support your knowledge and skill development for the third step of evidence based practice (EBP). As you practice using this information, it will become easier and faster to appraise the quality of a research study and to begin to apply the results to your practice. The first few appraisals that you complete may take a very long time. But just like acquiring any new skill, the appraisal process takes practice, and you will continue to improve the more you work at it.

APPRAISING RESULTS

Chapter 3 addressed the first two parts of Step 3. This chapter describes a process for appraising results and guides you through the appraisal. Chapter 4 covers the third and fourth parts:

C. Interpreting study results

D. Summarizing the clinical bottom line

This process includes the interpretation of statistics. The explanatory sections that follow include questions to consider when appraising the quality of an intervention study. There are five questions that help you organize the appraisal.

Interpreting the Results of an Intervention Study

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The results of intervention research studies are summarized in tables. Before trying to understand the text in the results section, it’s helpful to develop a habit of reading through the tables in a paper and reflecting on the information contained in them. The title of a table indicates its contents.

Descriptive Statistics

Figure 4.1 illustrates a typical table describing the demographic and clinical characteristics of the study sample for each group.1 Data are summarized using descriptive statistics. Descriptive statistics provides an overall impression of the typical values for a group as well as the variability within and between groups.2,3 First, look at the demographic data in the figure. Compare the unsupervised and supervised groups on average age, gender, ethnicity, ...

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