91Ó°ÊÓ

Dry eye is the most prevalent form of ocular discomfort and irritation, with approximately 20 million people in the United States having mild to moderate dry eye. A small clinical trial was performed to compare the effectiveness of an active drug vs. placebo for relieving symptoms of dry eye. Specifically, patients were randomized to either active drug or placebo for 2 weeks. They then came for a clinic visit where they were exposed to a chamber with a controlled adverse environment (CAE) for 90 minutes (with low humidity intended to exacerbate symptoms of dry eye). The patients were then asked to report their degree of discomfort while in the CAE using the following scale: \((0=\text { none, } 1=\) intermittent awareness, \(2=\) constant awareness, \(3=\) intermittent discomfort, \(4=\) constant discomfort). The results by treatment group are shown in Table 10.45 What is the difference between a nominal and ordinal categorical variable? What type of variable is ocular discomfort?

Step by step solution

01

Understanding Nominal Variables

Nominal variables are used to label or name categories without implying any order among them. Examples include gender, hair color, or types of cars. There is no inherent ranking or sequence in the categories.

02

Understanding Ordinal Variables

Ordinal variables are categorical variables that have a specific order or ranking. The difference between the values is not necessarily uniform, but the order is meaningful. Examples of ordinal variables include satisfaction ratings (such as 1-5 stars) or educational qualifications.

03

Identify Ocular Discomfort as a Variable

Ocular discomfort in this study is measured using a scale from 0 to 4, representing different levels of discomfort. Each number has a specific meaning, with 0 indicating no discomfort and 4 indicating constant discomfort.

04

Classify Ocular Discomfort

Since the ocular discomfort levels have a set order (from none to constant discomfort), this variable is an ordinal categorical variable. The numerical scale implies a ranking or sequence, thus fitting the definition of an ordinal variable outlined in Step 2.

Unlock Step-by-Step Solutions & Ace Your Exams!

• Full Textbook Solutions

  Get detailed explanations and key concepts

• Unlimited Al creation

  Al flashcards, explanations, exams and more...

• Ads-free access

  To over 500 millions flashcards

• Money-back guarantee

  We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

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

Nominal Variables

Nominal variables are a type of categorical variable. They help us understand categories without any particular order. Think of them as labels. A great way to imagine this is by considering the colors in a box of crayons. Whether "red" comes before "blue" or "green" doesn't matter. These colors are just names or labels. They don't imply a ranking.
Another common example involves hair color. People might be grouped into categories like "blonde," "brunette," and "redhead." Here, the categories don't follow an order. Nobody would say that "brunette" is higher or lower than "blonde." They merely identify types.
Nominal variables are essential in many research fields. They make it easy to categorize information without worrying about the order. Often, they are used in surveys or studies to collect basic demographic information.

Ordinal Variables

Ordinal variables also categorize data, but they have an order or ranking. This means that the categories follow a specific sequence. Let's consider a restaurant rating system: 1 star signifies a poor experience, and 5 stars mean excellent. Here, there's a clear progression from bad to good.
When we measure categories with ordinal variables, the distance between categories may not be uniform. For example, the gap between 1 star and 2 stars might feel different versus 3 stars to 4 stars.
An everyday example of ordinal variables could be clothing sizes like small, medium, and large. While they follow an order, the difference between "small" to "medium" isn't the same as "medium" to "large" in exact terms.
In many fields, especially in clinical and social sciences, ordinal variables help illustrate differences in how entities feel or perceive an experience. In the context of ocular discomfort, this means recognizing varying levels of discomfort from none to constant.

Clinical Trials

Clinical trials are essential for discovering new treatments and medicines. They involve systematically testing the effects of medical interventions on human subjects. Usually, participants in clinical trials are randomly assigned to different groups.
A notable part of clinical trials is the comparison between an active treatment group and a placebo group. This distinction helps determine how effective a treatment is.

• Active treatment group: Receives the experimental drug or therapy.
• Placebo group: Receives a non-active substitute, often called a sugar pill or saline shot.

This method ensures that the results are due to the treatment and not just by chance or placebo effect.
The study of dry eye using a scale from 0 to 4 to measure discomfort is an example of how clinical trials gauge treatment impact. Such studies often rely on either nominal or ordinal data to analyze findings. They help medical professionals better understand treatments' success or need for adjustments.