Chapter 4

### Pre-Test

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?

### Introduction

Chapters 3 and 4 support your knowledge and skill development for the third step of evidence based practice (EBP):

STEP 3: Critically appraise the research evidence for applicability and quality

Chapter 3 included parts A, Determining applicability, and B, Determining quality of a research study. This chapter includes parts

C. Interpreting study results and

D. Summarizing the clinical bottom line (Fig. 4.1).

###### FIGURE 4.1

Appraising the results of a study and the clinical bottom line.

Reading and interpreting study results can be challenging. If you develop a systematic approach to reading through the results of a study, it becomes easier and faster to interpret the study findings. This chapter describes a process for appraising results and guides you through the appraisal, including the interpretation of statistics.

#### Part C: Interpreting Results of an Intervention Study

##### Locating and Appraising the Results of a Research Study

Tables have it all! The results of intervention research studies are summarized in tables. A helpful habit to develop is to read through the tables in a paper and reflect on the information contained in them before trying to understand the text in the results section. The title of a table indicates what will be included in the main part of the table. Figure 4.2 illustrates a typical table describing the demographic and clinical characteristics of the study sample for each group.1

###### FIGURE 4.2

Typical table describing the demographic and clinical characteristics of the study sample for each group. From: Ylinen J, Takala EP, Nykanen M, et al. Active neck muscle training in the treatment of chronic neck pain in women: a randomized controlled trial. JAMA. 2003;289:2509-2516; with permission.

Data are summarized using descriptive statistics. Descriptive statistics give you an overall impression of the typical values for the group as well as the variability within and between the groups.2,3 First, look at the demographic data. Compare the control and the two training groups on average age, height, weight, and ...

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