人機交互理論與技術(shù)：Chap 2 Evaluation Methods

1、Chap 1 Design Principles (for GUI)Chap 2 Evaluation MethodsChap 3 GUI OptimizationUser Interface Development ProcessPart 3 GUI Design and EvaluationDesignPrototypeEvaluateChap 2 EvaluationUsability Principles2.1 User Study2.2 Predictive ModelsThe aim of exact science is to reduce the problems of nat

2、ure to determination of quantities by operations with numbers. - James Clerk Maxwell2.2 Predictive Models2.2.1 Fitts Law and Hicks Law2.2.2 GOMS Keystroke-Level Model2.2.3 Measurement of Interface Efficiency2.2.2 GOMS Keystroke-Level Model-Card et al., 1983: The Psychology of HCIGoals - the state th

3、e user wants to achieve e.g., find a websiteOperators - the cognitive processes & physical actions performed to attain those goals, e.g., decide which search engine to useMethods - the procedures for accomplishing the goals, e.g., drag mouse over field, type in keywords, press the go buttonSelection

4、 rules - determine which method to select when there is more than one availableGoals Operators Methods Selection rulesGOMS Model: how long will a user take to perform a particular operationGOMS Keystroke-Level Model2.2.2.1 Notations2.2.2.2 Interface Timings2.2.2.3 GOMS Calculations2.2.2.4 Examples2.

5、2.2 GOMS Keystroke-Level Model2.2.2.1 NotationsTap: pressing and releasing a keyClick: positioning the GID and then tapping the GID buttonDrag: pressing the GID button at one location and then moving the GID before releasing the GID button at a new locationDouble click: positioning the GID and then

6、tapping the GID button twice quickly2.2.2 GOMS Keystroke-Level Model immediately after the name of a key to indicate that the key has been pressed and to be held: Shift immediately after the name of a key to indicate the release of the key: Shiftt t , t , tA space separates the notation of consecuti

7、ve actionsA tap of the space bar is represented by the notation Spaces p a c e, ssppaaccee Shift n Control k Shift w ControlCommand Control Power Command Option p r Hold these keys and wait till a chime sounds -example on a Mac2.2.2.1 Notations, Denote keyboard operations2.2.2 GOMS Keystroke-Level M

8、odel2.2.2.2 Interface TimingsThe time it takes the user-computer system to perform a task is the sum of the times the system to perform the serial elementary gestures that the task comprises NamingTypical valuemeaningKeying，K0.2sTap a key on the keyboardPointing，P1.1sPoint to a position on a display

9、Homing，H0.4sUsers hand move from the keyboard to Mouse or other GID(Graphical Input Device) or from GID to keyboardMentally preparing，M1.35sPrepare mentally for the next stepResponding，RWait for a computer to respond to input2.2.2 GOMS Keystroke-Level Model2.2.2.3 GOMS CalculationsFiguring out at wh

10、at points the user will stop to perform an unconscious mental operation (M) Rule 0 Initial insertion of candidate MsInsert Ms in front of all KsInsert Ms in front of all Ps that select command (but not for any Ps that point to arguments of those commands)Rule 1 Deletion of anticipated MsIf an operat

11、ion symbol following an M is fully anticipated just previous to that M, delete the M. Pointing and clicking (you move the GID with the intent of tapping the GID button when you reach the target), PMK, PK2.2.2 GOMS Keystroke-Level Model2.2.2.3 GOMS CalculationsFiguring out at what points the user wil

12、l stop to perform an unconscious mental operation (M) Rule 2 Deletion of Ms within cognitive unitsIf a string of MKs belongs to a cognitive unit, delete the all the Ms but the first. a command name, an argument to a command: typing 4567.89Rule 3 Deletion of Ms before consecutive terminator If a K is

13、 a redundant delimiter at the end of a cognitive unit (such as the delimiter of a command immediately following the delimiter of its argument), delete the M in front of it.2.2.2 GOMS Keystroke-Level Model2.2.2.3 GOMS CalculationsFiguring out at what points the user will stop to perform an unconsciou

14、s mental operation (M) Rule 4 Deletion of Ms for the terminators of commandsIf a K is a delimiter that follows a constant string (such as command name or any typed entity that is the same every time you use it), delete it. But if the K is a delimiter for an argument string or any string that can var

15、y, then keep the M in front of it.Rule 5 Deletion of overlapped MsDont count any portion of an M that overlaps an R2.2.2 GOMS Keystroke-Level Model2.2.2.4 ExamplesDialog box for Temperature ConvertorGUI for Temperature ConvertorC= 5/9 X (F-32) F= C X 9/5 + 32Temperature ConvertorChoose which convers

16、ion is desired, then type the temperature and press Enter Convert F to C Convert C to F 2.2.2 GOMS Keystroke-Level ModelH (move hand to GID)HP (point to the desired radio button)HPK(click the radio button)HPKH (move hand back to keyboard)HPKHKKKK (type 4 characters)HPKHKKKKK (tap Enter)Rule 0: HMPMK

17、HMKMKMKMKMKRule 1、2、4: HMPKHMKKKKMK =0.4+1.35+1.1+0.2+0.4+1.35+4X(0.2)+1.35+0.2=7.15 : MKKKKMK = 3.7 (7.15+3.7)/2=5.4 secondTemperature ConverterChoose which conversion is desired, then type the temperature and press Enter Convert F to C Convert C to F 2.2.2 GOMS Keystroke-Level ModelHPK (move hand

18、to GID and click and hold down)HPKPK (continue move the arrow until it points to the correct value and release the GID button )Rule 0: HMPMKMPMKRule 1: HMPKPK =0.4+1.35+1.1+0.2+1.1+0.2=4.35 : considering scrolling operations, S=3HPKSKPKSKPKSKPKK Rule 0: H+3(M+P+K+S+K)+M+P+K+K 0.4+3X(1.35+0.2+3.0+0.2

19、)+1.35+0.4+0.2+0.2 =16.8 second2.2.2 GOMS Keystroke-Level ModelGive the GOMS Calculation of your Converter ProgramHand in your report before next classSupplemental ProjectThe aim of exact science is to reduce the problems of nature to determination of quantities by operations with numbers. - James C

20、lerk Maxwell2.2 Predictive Models2.2.1 Fitts Law and Hicks Law2.2.2 GOMS Keystroke-Level Model2.2.3 Measurement of Interface Efficiency2.2.3 Measurement of Interface EfficiencyHow fast you should expect an interface to be?2.2.3 Measurement of Interface EfficiencyHow fast you should expect an interfa

21、ce to be?The fastest possible interface We first determine a lower bound on the amount of information a user has to provide to complete the special taskThe amount of data conveyed by a communicationThis minimal amount is independent of the design of the interface2.2.3 Measurement of Interface Effici

22、encyInformation Efficiency E of an interface is defined as the minimum amount of information necessary to do a task the amount of information that has to be supplied by the user Emin=0, Emax=1 (similarly to efficiency defined in thermodynamics) E takes into account only the information required by t

23、he task and that supplied by the user. two or more methods may have the same E, yet different total times. a method with a higher E yet is slower than another method: MKMK vs MKKK for the most part, the more efficient interface is also the more productive interface2.2.3 Measurement of Interface Effi

24、ciency Information amount information is measured in bits; one bit represents a choice between two alternatives given n equally likely alternatives , the amount of information communicated by all of themExample: 1 choice made among 4 objects (A,B,C,D) requires 2 bits of information: 1st bit can choo

25、se A&B or C&D, 2nd can choose A or B (C or D). 2 binary choices, or 2 bits suffice to separate 1 item from a set of 4.For n, the amount of information communicated by all of them is the power of 2 equal to n: 2x=n 2.2.3 Measurement of Interface Efficiency Information amount information is measured i

26、n bits; one bit represents a choice between two alternatives given n equally likely alternatives , the amount of information communicated by all of them: log2n, any of them is with (1/n) log2n but not all are with the same probability (1/n), the ith alternative has probability p(i): p(i)log2(1/p(i)T

27、otally, information of n alternatives: p(i)log2(1/p(i)2.2.3 Measurement of Interface Efficiency Character Efficiency character efficiency is defined as the minimum number of characters required for a task, divided by the number of characters the interface makes the user enter if the possible message forms of the temperature converter are, -.dd, -d.d, .ddd, d.dd and dd.d convertor1 (dialogue) : 4/6=67% achieving an interface that required 4 keystrokes, will give us a character efficiency of 100% in GOMS, MKKKK=2.15s2.2.3