Assignment #2SI 688Fall 2010

Student ID: 5563 4294

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Question 1 For each of the following examples, describe someone for whom the chosen control would serve as an affordance and someone for whom it would not. Explain why in both cases.

In your answers, please be sure to demonstrate the following: That you know what an affordance is That you can name at least two types of reasons why something could be an affordance for

one person and not for another person.

1a) A door knob.1b) An underlined, blue word on a web page.1c) A shaded, slightly raised button on a dialog box with the word “Cancel” written on it.1d) The characters “$_” printed in white at the top left corner of an all-black screen.1e) An picture of a trashcan in the lower right corner of a screen containing a lot of other, similar-sized icons.

AnswerNorman defines affordance as "the perceived and actual properties of the thing…that determine just how the thing could possibly be used…taken advantage of, the user knows what to do just by looking." (Norman, 9).

1a) A doorknob suggests how it might be used by its size, shape, and positioning. The rounded shape suggests it can be rotated, while it's size is accommodating to a human hand and positioned at a level where it can easily be grasped for the action of rotation in addition to being placed on a portal or door.

It's hard to imagine anyone having difficulty with a doorknob since both closed doorways and knobs are so ubiquitous. I would gather that most adults would take these cues and grab a doorknob and see what they can do. But an individual used to living in wide open space without fixed portals might have some difficulty understanding the purpose, or a young child that stands below the doorknob (assuming he or she hasn't witnessed anyone using one).

1b) Underlined blue text on a simple web page takes advantage of visual salience to draw attention to itself. If such text doesn't actually draw the mouse to itself, it certainly draws the eye without much effort, since due to the gestalt principle of similarity "objects that look similar appear grouped" (Johnson, 14).

A person with some experience with pointing and clicking with a mouse would be used to finding things on screen to take action with. Someone without much computer experience might still see these blocks of text standout but wouldn't necessarily know what to do with them.

1c) Buttons likes this rely on perceived affordances, cue that mimic those from the real world and takes advantage of the physical affordances of the original object. This particular button attempts to imitate the light and shadow of a three dimensional protrusion which invites a push.

This sort of real world imitation would be helpful to someone with prior button pushing knowledge.

1d) Because it's on screen, there's no innate physical affordance to this glyph. Nor is there any perceived affordances either, since there's no real-world equivalent. This is an affordance that has to be learned through prior computing experience. A power user with some experience with command-line prompts might have a guess of what to do with it, whereas everyone else would probably stop and wait for the computer to provide some feedback.

1e) The real world metaphor here is clear: in the physical world, we throw things we don't want into the trash, so the perceived affordance is the same: we move things on our computer (the other pictures/icons on the screen) to this trash can. Or at the very least, that the surrounding pictures are trash around the can.

Users familiar with the visual appearance of trashcan can vary, a computer user from another country might not immediately take advantage of this cue.

Question 2

Watch the Apple “Knowledge Navigator” video:

http://www.youtube.com/watch?v=kl3CVaWtF-o&feature=related

Name two metaphors that the system implements to try to facilitate the user’s interaction with the system. Explain the schema(s) that are invoked by the metaphors and give an example from the video of how that schema helps the user know how to operate the system.

Be sure to demonstrate your understanding of what a schema is and how metaphors and schema are related to each other.

Answer

Metaphor 1: a bookThe computing device used is designed like a traditional book.

Schema:

Since a schema is "a mental concept or mental model…[that] organizes information into general structures, patterns, and forms" (Norman, 163) – it's wise to take advantage of existing collections of interactions for a new device or interface.

The book metaphor attempts to make device's interface easier to grasp by leveraging the (presumably) already existing schema of a book by the user. Books can be opened to begin the reading process; so too can the computing experience. The interface of the device takes advantage of other related concepts to the book schema:

Books are made of paper. The interface uses perceived affordances to suggest note pads and other uses of paper on top of the existing surface.

Books can be photo scrap books: the avatar is framed and bordered like a traditional portrait and is perceived as a sort of talking scrapbook photo, and other images are presented in a similar fashion like the map of Brazil.

Highlighting in books. Yellow color, like traditional yellow highlighting, is used to make pertinent information more salient.

Metaphor 2: Personal AssistantSchema:

A live human assistant is there to help, and ideally, do so in a personable manner. But going beyond merely being available, an assistant is expected to be helpful.

The knowledge navigator uses a human portrait as an avatar representing a personal assistant. It attempts to recreate the experience and expectations of a real person in many ways.

It methodically steps through reminders and important agenda items for the current context, doesn't speak rapidly and allows itself to be interrupted. It responds to spoken commands in a calm, unassuming manner, and manages to find answers for the user when asked, politely correcting when there's a mistake.

The alternative here would be eschew the human metaphor and simply present a more robotic or impersonal prompter, without the human face. It could have been, for example, the verbal and conversational equivalent of a DOS prompt, merely asking "what do you want to do next" rather than attempting to interact with the user in a humanistic way.

Question 3aFor each of the lists below, describe how you would estimate the length of time it would take to select an item. In particular, state whether the Hick-Hyman Law would provide a suitable estimate and, if so, provide the estimate1. For List #1, assume the user needs to select “Detroit” as a travel destination. For List #2, assume the user wishes to purchase a radar detector and wishes to see the price on one.

List #1 List #2Austin wanted ti-84 plus calculator Baltimore iPod Mini 2nd Gen 4GB (silver) w/ iPod Dock Boston ALPINE TYPE-R 12' 600RMS 1800WATTMP Charlotte Sony 51" WIDESCREEN TV - BIG SCREEN HDTV Chicago sony bloggie mhs-pm5 Columbus 2 mtx 12" subs with amp and box must sell today Dallas Kenwood 2 10's Good Condition! Denver WTB pci wifi cards Detroit Xbox 360 Wireless Adaptor El Paso 14" Magnavox TV Fort Worth DJ - Speakers Houston Toshiba - 37" LCD 1080p Indianapolis 16GB 3rd Gen. New with Warranty iPod Touch Jacksonville STEREO SPEAKERS Las Vegas BRAND NEW RADAR DETECTOR. Los Angeles 2010 TOPPS UPDATE ICHIRO ALL-STAR JERSEY MARINERS Louisville NEW BROTHER INTELLIFAX-1270e PLAIN PAPER FAX MACHINE Memphis 26 inch LCD TV! Milwaukee LCD TV WESTINGHOUSE FLAT SCREEN 1080 DPI Nashville Do you need Projection Tv Repair? New York Memorex DVD/CD Player Philadelphia NIKON CAMERA, LENS AND BAG Phoenix 2 10 Portland XBOX 360 & PS3 REPAIRS (RROD, YLOD, DISC WONT READ) San Antonio Ipod nano camera 8gb green San Diego (2) Audiobahn 12'' 4400watt!! San Francisco B&K/Epos stereo system San Jose 32gb Ipod touch 3g Seattle PS ONE Washington

1 If applying the Hick-Hyman Law, use the formulation provided in the Week 5 slides and use a=300 and b=200.

AnswerT = a + b log2(n+1)T = 200 + 300 • log2(n+1)

— where n = the number of choices available.—

The Hick-Hyman law applies to lists with "equally probable choices" (Wikipedia), and the base 2 logarithm assumes a binary search (ibid) – meaning the choices are meaningfully ordered.

List #1:The user will scan the list assuming the alphabetic arrangement, and be able to quickly eliminate choices that start after Detroit (the letter "D").

List #2:The list isn't ordered in any discernable fashion, and to some extend the choices aren't exactly "equally probable" given the different types of display (ALL CAPS, different line lengths, etc)

Because of all these factors, a user would basically have to scan the entire list serially and process every choice to find a radar detector. Even that is a hard proposition given the similarity of items around it. For this serial search it will take approximately "NT/2 seconds, in a self-terminating search where N is the menu size and T is the time to read each item" (Wickens Ch.3 , 82). Assuming N = 29, T = approximately 47ms for each word (Card, Moran, Newell, 43) and an average of 4.8 words per line here:

(29∗(4 .8∗47))/229∗225 . 6/26 ,542 /23 ,271ms

about 3 seconds of a diligent linear search?

Question 3bA user interface you are designing needs to present the user with a list of 64 countries from which to choose. Use the Hick-Hyman Law to determine whether it would it be more efficient to display this as a single list of 64 items or 8 lists of 8 items with the top level list showing the alphabetical range of each sublist (e.g., A-C, D-F,…) and the second-level list showing the country names themselves.

Assume the following: Users will be looking for a specific country and will not need to think about what it is. They will not require any “mental time” to identify the alphabetical range of the country

they’re looking for (e.g., if the country they are looking for is Belgium they will “instantly” identify A-C as the correct top level item).

You can ignore the time it would take to execute any necessary selections (e.g., clicking on a menu or country item).

No scrolling will be necessary.

Your answers to both 3a and 3b should demonstrate that you understand how and when to apply the Hick-Hyman Law. You should also demonstrate that you understand what other principles to apply to describe list selection in cases where Hick-Hyman does NOT apply.

AnswerWith an order list of 64 items, it would take approximately 2s:

Taking into account assumption 2 (no time to identify the header alphabetic range), it will be just a scan that list of eight items.

T=200+300 *log2(8+1)T=200+300∗3 .169925001442312T = 200 + 950T = 1150msT = 1 .15s

Therefore it's a bit faster to scan the lists with headers. Although if you assume that the user needs to scan the headers first, it would be two of these 1.15s operations, and might actually be slightly slower.

Question 4Laura and Lindsay have both been hired for a data entry position and will be required to learn a new system. Based on their cognitive abilities, sketch their relative learning curves and explain why the curves look different.

Your answer should demonstrate your understanding of the relationship between cognitive ability and skill acquisition.

Laura LindsayFluid Intelligence/Reasoning (Gf) 90 65Crystallized Intelligence/Knowledge (Gc) 92 52General (domain-specific) Knowledge (Gkn) 88 48Visual-Spatial Abilities (Gv) 72 72Auditory Processing (Ga) 66 68Short-term Memory (Gsm) 78 76Long-term Storage and Retrieval (Glr) 72 73Cognitive Processing Speed (Gs) 75 75Decision/Reaction Time or Speed (Gt) 71 72Psychomotor Speed (Gps) 49 91Quantitative Knowledge (Gq) 91 60Reading/Writing (Grw) 93 68Psychomotor Abilities (Gp) 56 88Olfactory Abilities (Go) 72 89Tactile Abilities (Gh) 77 81Kinesthetic Abilities (Gk) 73 78

AnswerThe factors that will matter more here are a) the ones that difference in score and b) ones that might directly impact performance of this particular position.

According to these two sites: http://www.evancarmichael.com/Home-Based-Business/1552/Necessary-skills-for-Data-

Entry-Workers.html) [car]http://www.bls.gov/oco/ocos155.htm [bls]

a data entry position involves:"need to be an organized person" [car]"typing and keyboarding skills" [ibid]"being able to figure out brand new programs without any supervision" [ibid]

"operate a variety of office machines" [bls]"proofread … for accuracy" [ibid]

Some cognitive factors matter more for these particular skills and will affect the individuals' learning curves. In particular:

Gf: Necessary for approaching new situations and devices. Gkn: High scores here indicate learned and practiced skills. Gsm: Short term memory is important for transferring data from one source to another.Gs: High-focus execution of "automatic tasks" is driven by this skill (i.e. typing) Gps: Typing requires fine motor control. Gq: This involves procedural memory, for repeating tasks of the job.Grw: Processing of words/forms/verbal input.Gh: To some extent, high tactile abilities might mean a better touch typist.

Because Laura excels in the area of Fluid Intelligence, she will likely quickly pick up on new systems used on the job. Her higher scores of Crystallized Intelligence and Domain specific Knoweldge will help her hit the ground running quickly. She also has higher scores of Quantitative Knowledge and Reading/Writing that will make her initial learning curve fast, and the skill improvement to taper off as time goes on.

By Contrast, Lindsay falls short of Laura in all of the aforementioned areas, but she excels at Psychomotor speed and Psychomotor Abilities. She also has a slight leg up on Tactile abilities. As a result, she will be able to do the job competently but will likely have a harder time getting up to speed. Her initial skill improvement starts off slow, increases and gradually tapers off.

Question 5

There are two ways to insert a formula into a Google Spreadsheet. One is to type the formula in directly, along with its arguments. Another is to select the formula from the “Insert | Formula” menu and then select the range for the parameters. Assume you wish to insert a formula to find the average of 10 numbers that have already been input into the spreadsheet. Use a KLM analysis to determine which method would be the most efficient for adding the formula.

Use the Keiras’ guidelines for applying mental operators, which can be found in the GOMS tutorial under CTools/Resources.

Your answer should demonstrate that you know how to apply the KLM to estimate the human performance of a system. You should clearly state any additional assumptions you need to make in order to answer this question.

AnswerTyping in the formula directly.Assumptions:

a) the numbers were entered by hand, so the last return keystroke puts the focus on cell A12.

b) For this task, there's no movement from the keyboard to the mouse (i.e. no homing operations)

c) The following times are used for operations

Keystroking (0.28)Pointing (1.1)Button on the mouse (0.1)Homing (0.4)Mental work (1.2)

Op T DescriptionM 1.2 Recall Formula to use ("AVERAGE")M 1.2 Recall syntax for functions (use of "=", (x:y) 6K 0.28*16 Type "=average(a2:a11)" + return

6.88s

Using the menu functionsAssumptions:

a) the numbers were entered by hand, so the last return keystroke puts the focus on cell A12.

Op T DescriptionM 1.2 Recall menu structure, What menu to use ("insert")H 0.4 Move from keyboard to mouseP 1.1 Move cursor from last position to insert menuBB 0.2 Click and release on insert menuM 1.2 Recognize menu item "function"P 1.1 Move cursor from parent menu to function menuM 1.2 Recognize "AVERAGE" submenuP 1.1 Move cursor over to submenu AVERAGEBB 0.2 Click on menu item AVERAGEH 0.4 Move back to keyboardK 0.28*7 Type "a2:a11" + return to enter cell range

10.06s

Given this analysis, the keyboard entry method is almost twice as fast.

Question 6You are consulting on a project to design a new blog management system aimed at K-12 students. One of the software developers on the project has raised an issue with the current design that she believes needs to be fixed: if an author changes their “signature” it will only apply to future blog posts—it will not be retroactively applied to posts that were made in the past. She is proposing a change to the design that would force the “signature” to apply to all posts. Moreover, she is arguing that the signature editor should be changed to allow users to include several “macros” in their signatures including the current date, current time, geographical location of the author, total number of posts the author has made up to that point, PageRank of the author’s site, and several other computed values.

Describe the design dilemma being presented by the developer in terms of the Cognitive Dimensions Framework to help clarify the discussion. You do not need to provide a recommendation, your job is just to reformulate the discussion.

Your answer should demonstrate that you understand several cognitive dimensions, that you know how to apply them to the analysis of an interactive system, and that you understand how to use them to describe design tradeoffs.

AnswerThe system currently suffers from a lack of viscosity, specifically repetition viscosity. The blog signatures can't be retroactively applied to the entire blog automatically. Instead, each previous blog post must be edited by hand. Doing so can lead to manual errors in the process.

The proposed change introduces the ability to automatically update all instances of the blog signatures at once, which will mitigate the need to repetitively change all the signatures (assuming this is the desired result).

This reduction in viscosity introduces a small hidden dependency. Each individual signature is not a unique one, but instead tied to a "global" signature, and this dependency may not be entirely clear to other users of the system. It's possible that a user may not want all signatures to be updated, unless this link between signatures and all blog posts is made explicit.

The introduction of a macro system creates an abstraction — a grouping of metadata about each post. This has potential to add useful metadata to blog posts, but in doing so it introduces a level of complexity that might be intimidating to some users in spite of the potential added utility. Do users of the this system care about PageRank, or GeoTagging? It may be adding more confusion unless the system remains abstraction-tolerant. If posts require such metadata to be entered, the system would be abstraction-hungry and would frustrate users without any use or desire for such metadata. Instead, it would be better to allow the system to accept some macro abstraction if desired. The alternative would be the current system, which is assumed to be abstraction-hating; it currently does not accept any metadata grouping to be added to posts.

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Since metadata like date stamping and geotagging are tied to each post, but can't be assumed to be linked together across posts, there is potentially knock-on viscosity being introduced to the system. If a user wants to change several geotags or date stamps, will they have to track down all the posts and change them individually?

Question 7Drawing on your understanding of human cognition, explain why the cognitive dimension of consistency is important in interactive systems.

Your answer should demonstrate that you understand the cognitive foundations for this particular cognitive dimension, and should draw on readings from earlier in the course.

AnswerBlackwell defines consistency as " similar semantics are expressed in similar syntactic forms" [Blackwell, 39] and further states that "consistency … affects learnability" [ibid]. What if, when learning a complex program, every step of the way introduced completely different icons, grouping, layouts — all for no apparent reason? If all of the dials on my Sync car radio functioned differently across the various functions the result would be disastrous: it would tax working memory unnecessarily because it would force me to recall the current function context and how the dial should behave for every operation. It would also greatly increase the learning curve to learn what the dials would do in every context.

In situations such as these, the lack of a constant behavior, function or appearance can create all sort of proactive interference, thus impeding learning of the system.

Consistency can help searching in general: a lack thereof requires users to serially search for targets. In the latter case consistency can be alphabetical listings or visual hierarchies that eliminate the need to sort through all the clutter.

Further, a runaway lack of consistency on a system requiring supervisory control would undermine the use of the system. In this case consistency is parallel to similarity and gestalt grouping, where common functions are lumped together. Grouping help with working memory loads when conduct supervisory scans by eliminating the need to serially scan each individual item. On top of that if all the controls had different typefaces and readout styles it would require extra effort to process each one.