Fall 2004 6 831 UI Design and Implementation 1 1 Fall 2004 6 831 UI Design and Implementation 2 Today s candidate for the Hall of Fame Shame is the Alt Tab window switching interface in Microsoft Windows This interface has been copied by a number of desktop systems including KDE Gnome and even Mac OS X The first observation to make is that this interface is designed only for keyboard interaction Alt Tab is the only way to make it appear pressing Tab or Shift Tab is the only way to cycle through the choices If you try to click on this window with the mouse it vanishes The interface is weak on affordances and gives the user little help in remembering how to use it But that s OK because the Windows taskbar is the primary interface for window switching providing much better visibility and affordances This Alt Tab interface is designed as a shortcut and we should evaluate it as such It s pleasantly simple both in graphic design and in operation Few graphical elements good alignment good balance The 3D border around the window name could probably be omitted without any loss This interface is a mode since pressing Tab is switching between windows rather than inserting tabs into text but it s spring loaded happening only as long as the Alt button is held down This springloading also provides good dialog closure Is it efficient A common error when you re tabbing quickly is to overshoot your target window You can fix that by cycling around again but that s not as reversible as just moving backwards with a mouse You can also back up by holding down Shift when you press Tab but that s not wellcommunicated by this interface and it s tricky to negotiate while you re holding Alt down There is one common operation that Alt Tab supports wonderfully toggling back and forth between two windows 2 User testing Ethics Formative evaluation Fall 2004 6 831 UI Design and Implementation 3 In this lecture and the next one we ll talk about user testing putting an interface in front of real users There are several kinds of user testing but all of them by definition involve human beings who are thinking breathing individuals with rights and feelings When we enlist the assistance of real people in interface testing we take on some special responsibilities So first we ll talk about the ethics of user testing which apply regardless of what kind of user test you re doing The rest of the lecture will focus on one particular kind of user test formative evaluation which is a user test performed during iterative design with the goal of finding usability problems to fix on the next design iteration Next lecture we ll look at another kind of user test a controlled experiment 3 Design Task analysis Design heuristics Evaluate Heuristic evaluation Today User testing Fall 2004 Implement 6 831 UI Design and Implementation Prototyping Toolkits 4 Here s a quick review of the iterative design process and the parts of it we ve seen so far The only evaluation technique we ve discussed so far has been heuristic evaluation Today we re looking at user testing which is more expensive and time consuming than heuristic evaluation but produces better results 4 Formative evaluation Find problems for next iteration of design Evaluates prototype or implementation in lab on chosen tasks Qualitative observations usability problems Field study Find problems in context Evaluates working implementation in real context on real tasks Mostly qualitative observations Controlled experiment Tests a hypothesis e g interface X is faster than interface Y Evaluates working implementation in controlled lab environment on chosen tasks Mostly quantitative observations time error rate satisfaction Fall 2004 6 831 UI Design and Implementation 5 Here are three common kinds of user tests You ve already done a formative evaluation on Prototype Testing Day when you had some of your classmates test your paper protoypes The purpose of formative evaluation is finding usability problems in order to fix them in the next design iteration Formative evaluation doesn t need a full working implementation but can be done on a variety of prototypes This kind of user test is usually done in an environment that s under your control like an office or a usability lab You also choose the tasks given to users which are generally realistic drawn from task analysis which is based on observation but nevertheless fake The results of formative evaluation are largely qualitative observations usually a list of usability problems Note that Prototype Testing Day was not the best way to do formative evaluation first because your classmates are probably not representative of your target user population and second because we had artificial time constraints that raised the pressure on users and experimenters prevented using substantial tasks and didn t allow for much debriefing or discussion after the test Better user tests would be use appropriate users and be more relaxed which we ll see later in the lecture A key problem with formative evaluation is that you have to control too much Running a test in a lab environment on tasks of your invention may not tell you enough about how well your interface will work in a real context on real tasks A field study can answer these questions by actually deploying a working implementation to real users and then going out to the users real environment and observing how they use it We won t say much about field studies in this class A third kind of user test is a controlled experiment whose goal is to test a quantifiable hypothesis about one or more interfaces Controlled experiments happen under carefully controlled conditions using carefully designed tasks often more carefully chosen than formative evaluation tasks Hypotheses can only be tested by quantitative measurements of usability like time elapsed number of errors or subjective satisfaction We ll talk about how to design controlled experiments in the next lecture 5 Users are human beings Human subjects have been seriously abused in the past Nazi concentration camps Tuskegee syphilis study MIT Fernald School study feeding radioactive isotopes to mentally retarded children Yale electric shock study Research involving user testing is now subject to close scrutiny MIT Committee on Use of Humans as Experimental Subjects COUHES must approve research related user studies Fall 2004 6 831 UI Design and Implementation 6 Let s start by talking about some issues that are relevant to all kinds of user testing
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