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Nurse-practitioners are nurses with advanced qualifications who often act much like primary-care physicians. Are they as effective as doctors at treating patients with chronic conditions? An experiment was conducted with 1316 patients who had been diagnosed with asthma, diabetes, or high blood pressure. Within each condition, patients were randomly assigned to either a doctor or a nurse-practitioner. The response variables included measures of the patients' health and of their satisfaction with their medical care after 6 months. \(^{44}\) (a) Which are the blocks in this experiment: the different diagnoses (asthma, and so on) or the type of care (nurse or doctor)? Why? (b) Explain why a randomized block design is preferable to a completely randomized design here.

Short Answer

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(a) The blocks are the different diagnoses: asthma, diabetes, and high blood pressure. (b) A randomized block design controls variability from diagnoses, ensuring more reliable comparisons between nurse-practitioner and doctor effectiveness.

Step by step solution

01

Understanding the Concept of Blocking

In experimental design, blocking is used to control for variability among subjects that can affect the outcome of the experiment. Blocks are groups where subjects have similar characteristics. When identifying blocks, we choose factors that are expected to influence the response but are not the primary treatment of interest.
02

Identify Potential Blocks in the Experiment

In the given experiment, there are two groups: the type of care (nurse or doctor) and the patient's condition (asthma, diabetes, or high blood pressure). The experiment is focused on assessing the effectiveness of nurse-practitioners versus doctors, so the primary treatment factor is the type of care, not the diagnosis.
03

Determine the Actual Blocks

The blocks in this experiment are the different diagnoses: asthma, diabetes, and high blood pressure. This is because these conditions can exhibit different patient responses and could introduce variability that might confound the results of the treatment comparison (nurse vs. doctor).
04

Reasoning for Choosing Blocks

Blocking by diagnosis helps to ensure that the effectiveness comparison between doctors and nurse-practitioners is not skewed by the inherent differences in patient outcomes due to different medical conditions. This allows each condition's specific variability and patient responses to be controlled or accounted for.
05

Advantages of Randomized Block Design

A randomized block design is preferable because it allows us to isolate and understand the effect of the primary treatment (type of care) while controlling for variability from known sources (like different diagnoses). It decreases variability within treatment comparisons and increases the precision of the experiment.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Randomized Block Design
In experimental design, a Randomized Block Design (RBD) is a potent technique used to control variability within an experiment. When researchers want to compare treatments, like in our case with doctors versus nurse-practitioners, it's crucial to neutralize any variability from extraneous factors. This is precisely where blocking comes in.

In a randomized block design, subjects are divided into blocks based on attributes expected to influence the outcome, yet are not central to the treatment focus. In the given study, patients were categorized by their chronic condition—either asthma, diabetes, or high blood pressure. These conditions form the blocks.
  • The primary treatment was the type of care (doctor versus nurse-practitioner).
  • The blocking factor aimed to control variability due to different diagnoses.
By organizing the study this way, researchers could more accurately attribute differences in patient health outcomes to the type of care rather than differences in baseline health conditions.
Response Variables
Response variables are the specific outcomes or measurements that researchers examine to assess the effect of treatments in an experiment. In the nurse-practitioner versus doctor experiment, response variables play a crucial role in evaluating success.

For this study, the response variables included:
  • Patients' health measurements: This likely included changes in symptoms, control over chronic conditions, and possibly additional metrics like blood pressure and blood sugar levels.
  • Patient satisfaction: Assessing how satisfied patients were with the care indicated the subjective and perceived success of treatment.
Considering both objective and subjective response variables offers a holistic view of the treatment's efficacy.
Chronic Conditions
Chronic conditions like asthma, diabetes, and high blood pressure present long-term healthcare challenges that require ongoing management rather than immediate cure. Patients with these conditions may have varied responses to medical interventions.

Chronic conditions often require:
  • Continuous medical monitoring and adjustments to treatment plans.
  • Care coordination among healthcare professionals.
In the study, categorizing patients by their chronic conditions allowed for an understanding of how these variables could affect treatment effectiveness independently of the healthcare professional involved.
Health Outcomes
Health outcomes are the end results of medical care, reflecting the treatment's effectiveness on patients' health condition. Analyzing health outcomes is essential in any healthcare-focused experiment to determine the true utility of the type of care provided.

In this study, health outcomes likely included criteria like:
  • Medical improvements or stabilization in chronic conditions, measured by objective health metrics.
  • Quality of life evaluations, which might involve reports on physical and emotional well-being.
The assessment of health outcomes helps identify which type of care—doctor or nurse-practitioner—is more effective in managing chronic conditions. Understanding and improving health outcomes leads to more personalized and effective treatment strategies.

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Most popular questions from this chapter

Dr. Linda Stern and her colleagues recruited 132 obese adults at the Philadelphia Veterans Affairs Medical Center in Pennsylvania. Half the participants were randomly assigned to a lowcarbohydrate diet and the other half to a low-fat diet. Researchers measured each participant's change in weight and cholesterol level after six months and again after one year. Explain how each of the four principles of experimental design was used in this study.

You have been invited to serve on a college's institutional review board. You must decide whether several research proposals qualify for lighter review because they involve only minimal risk to subjects. Federal regulations say that "minimal risk" means the risks are no greater than "those ordinarily encountered in daily life or during the performance of routine physical or psychological examinations or tests." That's vague. Which of these do you think qualifies as "minimal risk"? (a) Draw a drop of blood by pricking a finger to measure blood sugar. (b) Draw blood from the arm for a full set of blood tests. (c) Insert a tube that remains in the arm, so that blood can be drawn regularly.

Two essential features of all statistically designed experiments are (a) compare several treatments; use the double-blind method. (b) compare several treatments; use chance to assign subjects to treatments. (c) always have a placebo group; use the double-blind method. (d) use a block design; use chance to assign subjects to treatments. (e) use enough subjects; always have a control group.

Some Internet service providers (ISPs) charge companies based on how much bandwidth they use in a month. One method that ISPs use for calculating bandwidth is to find the 95th percentile of a company's usage based on samples of hundreds of 5 -minute intervals during a month. (a) Explain what "95th percentile" means in this selting. (b) Which would cost a company more: the 9th percentile method or a similar approach using the 98 th percentile? Justify your answer.

A study sought to determine whether the ancient Chinese art of acupuncture could help infertile women become pregnant.' One hundred sixty healthy women undergoing assisted reproductive therapy were recruited for the study. Half of the subjects were randomly assigned to receive acupuncture treatment 25 minutes before embryo transfer and again 25 minutes after the transfer. The remaining 80 subjects were instructed to lie still for 25 minutes after the embryo transfer. Results: In the acupuncture group, 34 women became pregnant. In the control group, 21 women became pregnant. (a) Why did researchers randomly assign the subjects to the two treatments? (b) The difference in the percent of women who became pregnant in the two groups is statistically significant. Explain what this means to someone who knows little statistics. (c) Explain why the design of the study prevents us from concluding that acupuncture caused the difference in pregnancy rates.

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