Section 2: Usability Defined

Usability Defined

Unit 1, Section 2, Overview

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Video Transcript
Hi, I’m Dr Anthony Chow and welcome to Section 2, Usability Defined. In this section, we’ll take a look at how usability is formally defined and the major factors that make up its definition.

Let’s begin. The International Organization for Standardization formally defines usability as the extent to which the product can be used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use. In other words, how effective, efficient, and satisfying is something to use to accomplish what we want?

Having a formal definition that is widely accepted and recognized allows us to focus clearly on usability’s three main factors: effectiveness, efficiency, and satisfaction.

Effectiveness is defined by the ISO standard as the percentage of goals achieved, the percentage of users successfully completing tasks, and average accuracy of completed tasks. In other words, can we achieve our goals with high levels of success with minimal effort? We will further break down effectiveness to a more granule level in just a second.

Efficiency is formally defined as the time to complete a task, task completed per unit time, and monetary cost of performing the task. In other words, how quickly and cost effectively can I complete a task or find what I am looking for? Again, we will more precisely define efficiency a little further on in this module.

Let’s walk through an example using UNCG’s website. Let’s say we’re looking for my contact information. Effectiveness. Can I find Dr Chow’s contact information? Efficiency. Can I do with minimal effort and error free? And satisfaction. Is the overall experience satisfactory?

Well, let’s see. From the home page, I quickly locate the search feature in the upper right hand of the page, which is where I would expect to find it. I enter the search term, Anthony Chow, faculty. I hit search, and what do I get? The first link is Dr Anthony Chow, which looks good. In fact, three of the four links look very promising.

Let’s select the first link and see what we get. Voila! There I am, with my phone number and email address clearly displayed. Mission accomplished with minimal effort and high return on investment with only three clicks. Overall satisfaction is also high, as the graphic design is clean, well branded, and does not distract me from my task at hand. This is a great example of high EAS for this specific task.

Okay, now that we have an initial feel of what usability is and what it looks like, let’s dig deeper and even more precisely to find each usability factor. Patrick Jordan. . . .More precisely to find each of the three formally defined factors of usability, effectiveness, efficiency, and satisfaction. In 1998, [Patrick Jordan] and I adapted his definition into an 8-factor usability scale, which we’ll use later on.

Effectiveness—or the extent to which a goal or task is reached—can be broken down into two subfactors: task completion and quality of output. In other words, were you or a user able to complete the tasks you were trying to accomplish and, if so, what was the overall quality of that output? These two subfactors can be used as an operational definition for effectiveness. Efficiency or the amount of effort required to accomplish a goal can be further broken down into four sub factors, the first is to what extent did you or a user deviate from the critical or most direct path towards attaining your goal, was it straight from point A to point B, or did you take a more circuitous route. The second is error rate, how many errors or false starts did you make before attaining your goal. And the third is time on task, how quickly were you able to accomplish your goal. And lastly, the fourth sub factor is mental workload, how hard did you have to work mentally to obtain your goal. Satisfaction, is a level of comfort the user feels in being able to accomplish a goal, and it can be defined by two sub factors, a quantitative rating of satisfaction and a qualitative description of that satisfaction. In research quantitative and qualitative data is considered the proverbially 1, 2 punch that allows us to measure and compare ratings as well as understand the reasons behind those ratings.

I use a scale of 1 to 10, which most people are familiar with, and can be equated with a percentage degree of satisfaction. The qualitative comments allow us to determine why users rate something the way that they did. All together then we have 8 total factors of usability that can be independently measured. We have two for effectiveness, task completion and quality of output. We have four for efficiency, deviations from the critical path, error rate, time on task, and mental workload, and we have two for satisfaction, a quantitative satisfaction rating along with qualitative comments. Ok, that’s it for this module, be sure to answer the five review questions as well as participate in the modules discussion questions and hands on activities. I hope to see you soon in another module.