Statistics Exercises for Chapter 21 and 45 (2 Articles, 20 Problems) based on RESEARCH ARTICLES: Rakel, B., & Frantz, R. (2003). and Porter, S. C., Fleisher, G. R., Kohane, I. S., & Mandl, K. D. (2003).

Exercises for Chapter 21

RESEARCH ARTICLE

Source: Rakel, B., & Frantz, R. (2003). Effectiveness of transcutaneous electrical nerve stimulation on postoperative pain with movement. The Journal of Pain, 4 (8), 455–64.

Introduction

Rakel and Frantz (2003) examined the effectiveness of transcutaneous electrical nerve stimulation (TENS) as an adjunct to pharmacologic analgesia on postoperative pain with movement after abdominal surgery. They also evaluated its impact on patients’ pain, vital capacity maneuvers, and walking parameters, such as gait speed, gait distance, and the level of assistance required. Three pain control strategies were randomly assigned to each of the first 3 ambulations on a postoperative day: (1) pharmacologic analgesia and TENS, (2) pharmacologic analgesia and placebo TENS, and (3) pharmacologic analgesia alone. TENS electrodes were applied parallel to the incision on both sides, and the frequency was self-adjusted by patients to as high a level as they could tolerate. Patient frequency selections ranged between 3 and 57 mA. Based on the TENS frequency they used, the patients (N = 33) were divided into 2 groups: a high frequency group (≥ 9 mA) and a low frequency group (≤ 8 mA). Use of TENS resulted in significantly lower pain intensity ratings during walking and vital capacity maneuvers, and faster gait and greater gait distances than with using analgesia alone. The patients’ pain with movement was measured with a vertical 21-item numeric rating scale (NRS) during transfer from lying to sitting position, walking, and performing vital capacity maneuvers. These data were analyzed with means and standard deviations, which are presented in Table 1.

Relevant Study Results

“A prospective, randomized, repeated measures design was used. Subjects served as their own controls… An estimation of desired sample size for dependent groups was determined by using pain intensity scores of the first 13 study subjects. On the basis of the effect sizes ranging between 0.22 for TENS versus placebo TENS and 0.77 for TENS versus pharmacologic analgesia alone, a moderate effect size was assumed… α = .05 and power = .7 required a sample size of 24 subjects” (Rakel & Frantz, 2003, p. 456). “The highest effect was between TENS and pharmacologic analgesia for pain during vital capacity (–0.58), followed by pain during gait speed (–0.47). The lowest effect sizes were between placebo TENS and pharmacologic analgesia alone for pain during gait speed (–0.03) and pain during transfer (0.08)” (p. 459).

TABLE 1 Descriptive Statistics for Pain Intensity During Transfer, Gait Speed, Gait Distance, and Vital Capacity

Rakel, B. Frantz, R. (2003). Effectiveness of transcutaneous electrical nerve stimulation on postoperative pain with movement. The Journal of Pain, 4(8), p. 459. Copyright © 2003, with permission from The American Pain Society.

1. Why did researchers choose to include a placebo TENS group in this study?

2. In Table 1, which movement maneuver was least painful for control subjects in the low amplitude group? Provide a rationale for your answer.

3. Using data presented in Table 1, calculate the ES of TENS for the total sample subjects’ pain intensity during transfer. Show your calculations and round your answer to two decimal places. Was the result significant? Provide a rationale for your answer.

4. How would you characterize the ES calculated in Question 3?

a.Small

b.Medium

c.Large

d.Non-existent

5. Based on the description of the sample size determination procedure provided in the Relevant Study Results, what was the most likely reason for the absence of significant differences between the levels of pain intensity of the experimental and the control groups undergoing the transfer procedure? Provide a rationale for your answer.

6. Using data presented in Table 1, calculate the ES of TENS for the total sample subjects’ pain intensity during the gait speed maneuver. Show your calculations and round your answer to two decimal places. Was the result significant? Provide a rationale for your answer.

7. Does the fact that the highest effect sizes were observed between TENS/pharmacologic analgesia and pharmacologic analgesia alone and the lowest effect sizes were between placebo TENS/pharmacologic analgesia and pharmacologic analgesia alone (see the Relevant Study Results) strengthen or weaken the validity of the research hypothesis of this study? Provide a rationale for your answer.

8. Why did researchers divide the TENS group into the low and high amplitude groups?

a. To compare the effects of both low and high amplitude TENS on patients’ pain intensity during different maneuvers.

b. To prove that only TENS set at high amplitude should be used as an adjunct therapy to pharmacological analgesia.

c. To show that the subjects of the high amplitude group did not need pharmacologic analgesia to control their pain.

d. By taking a closer look at the study, it is evident that the high amplitude group served as an experimental group while the low amplitude group served as a control group in this study.

9. What does it mean to design a study with a power of 1? Is this possible? Provide a rationale for your answer.

10. Based on the description of the study design presented in the Relevant Study Results, what does “subjects served as their own controls” mean?

Statistics Exercise 45

RESEARCH ARTICLE

Source: Porter, S. C., Fleisher, G. R., Kohane, I. S., & Mandl, K. D. (2003). The value of parental report for diagnosis and management of dehydration in the emergency department. Annals of Emergency Medicine, 41 (2), 196−205.

Introduction

Porter et al. (2003) conducted a prospective observational study to assess the predictive value of parents reporting the medical history and physical signs of dehydration in their children. Their study included 132 parent-child dyads. The primary outcome was percentage of dehydration, and the secondary outcomes were clinically important acidosis and hospital admission. They also compared the reports of physical signs of dehydration made by the parents and the nurse. Their study results indicated that parents’ report of physical symptoms and history had a higher sensitivity (range 73% to 100%) than specificity (range 0% to 49%) for predicting dehydration of 5% or greater in their child (Porter et al., 2003, p. 196).

Relevant Study Results

The researchers presented the results of their study in table format. Table 3 displays the results from the parents’ reported history, and Table 4 displays the comparison of the diagnostic value of the parents’ and nurses’ physical assessment of the clinically important signs of dehydration.

TABLE 3 Value of Parent-Reported History for Prediction of Clinically Important Dehydration

TABLE 4 Diagnostic Value of Parents and Nurses’ Report of Physical Signs for Clinically Important Dehydration*

EXERCISE 45 Questions

1. In Table 4, which two physical signs used by the parents to assess dehydration were the most sensitive? Provide a rationale for your answer.

2. In Table 4, which two physical signs used by the parents to assess dehydration were the most specific? Discuss the meaning of the specificity of these two physical signs.

3. In Table 4, for which physical signs of dehydration did the nurses have more true positives than the parents?

4. In Table 4, which physical signs of dehydration did the nurses have more true negatives than the parents?

5. In Table 4, what is the percentage of false negatives for dehydration if the parents reported Decreased tears? Please provide your calculations.

6. What does it mean if a screening test is 100% sensitive, as Decreased tears was when reported by nurses?

7. What is your interpretation of the specificity of Ill appearance as an indicator for clinical dehydration?

8. Were the nurses or the parents more sensitive and specific in the reporting of the physical signs of dehydration? Was this an expected finding?

9. Fill in the table below using the results from Table 4.

10. Fill in the table below using the results from Table 4.

The end--