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Introduction to KLM Operators
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Today, we are diving into the Keystroke-Level Model, or KLM. This model helps us predict how fast users can complete tasks by breaking them down into fundamental actions. Who can tell me what we call these actions?
Are they called operators?
Exactly! Operators are the basic actions. Let's discuss them in detail. The first operator is K, or Keystroke. Can anyone guess what that entails?
It must be about pressing keys, right?
That's right! Pressing a key is K. The time for this can vary significantly based on user skill level. An expert typist might take around 0.08 seconds per keystroke. So, shall we remember this as 'K for Keys'? Letβs move to the next operator, P for Pointing.
Exploring Pointing and its Implications
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Now, let's discuss P for Pointing. This operator is crucial as it describes the action of moving a mouse or a similar device to select something on the screen. How long do you think it takes on average?
Maybe around a second?
Close! On average, it takes about 1.1 seconds. This includes the moment to select the target. Remember, 'P for Pointing is 1.1 seconds!' Now, what do you think happens when the distance to the target increases?
It probably takes more time!
Exactly! Greater distances lead to longer pointing times, so keep that in mind when designing interfaces.
Understanding the Mental Preparation Operator
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Let's look at the M operator, or Mental Preparation. This one is a bit more abstract. Who can give an example of mental preparation in a task?
Maybe when we're planning out what to type next?
Right! Before typing, users often spend time thinking things through. The average time for Mental Preparation is 1.35 seconds. To help remember this, think 'M for Mind-Planning: the average is 1.35 seconds!' But mental preparation can be tricky, and it involves different heuristics, as weβll discuss next.
The Additive Nature of KLM
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Now, how do all these operators fit together in the KLM? It's all about summation. Can anyone explain what additive means in this context?
It means we add all the times together to find the total task completion time.
That's correct! The total predicted execution time for a task is simply the sum of the times of all the fundamental operations. Always remember: add them up for the total! KLM gives us a solid foundation for understanding user performance.
Putting It All Together
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In summary, today weβve discussed the fundamental operators of KLM: K for Keystroke, P for Pointing, M for Mental Preparation, and more. Why do we need to know them?
They help us predict how fast users can complete tasks and improve designs!
Exactly! Each operator offers insights that can optimize our interface designs. Letβs remember our key takeaways: KLM simplifies predicting user interaction times by breaking tasks into manageable pieces, which we can analyze for better design.
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
The Keystroke-Level Model (KLM) is an analytical framework designed to predict expert users' task execution times in Human-Computer Interaction through a series of defined fundamental operators. This section thoroughly explains each operator's properties, typical execution times, and context for application, highlighting their importance in optimizing interface design.
Detailed
Exhaustive Definition of KLM's Fundamental Operators
The Keystroke-Level Model (KLM), a cornerstone of predictive modeling in Human-Computer Interaction (HCI), fundamentally decomposes user tasks into a finite set of operators that represent observable actions. This section elaborates on KLM's core operators, which facilitate the prediction of task execution times based on rigorously established parameters. The operators are:
- K (Keystroke): This operator denotes the act of pressing any key on an input device, with execution times ranging significantly based on user typing skill.
- Typical Time: Approximately 0.08 seconds for expert typists to 1.20 seconds for novice users.
- P (Pointing): Represents the action of moving a pointing device (e.g., mouse) to select a target on the screen.
- Typical Time: 1.1 seconds, including the action to select upon reaching the target (using aggregated empirical studies).
- H (Homing): Captures the time taken to transition the userβs hand between input devices, for instance, from keyboard to mouse.
- Typical Time: 0.4 seconds, accounting for the physical grab and release of different devices.
- D (Drawing): Models the time to draw a sequence of straight-line segments with a pointing device, more relevant in graphic design contexts.
- Typical Time: 0.9n + 0.16 seconds, with βnβ representing drawn segments.
- M (Mental Preparation): Abstractly indicates the time users spend in cognitive processes required to plan or make decisions during interactions. This is often the most variable operator, applied using heuristics.
- Typical Time: Averages around 1.35 seconds, subject to complexity and cognitive load.
- R (System Response): Reflects the time the system takes to respond to user commands, varying extensively based on system performance.
This section emphasizes the additive nature of KLM. The total predicted time for task execution is derived by summing the time durations of these fundamental operators. In summary, understanding these operators enhances designersβ abilities to predict user performance and optimize interface designs efficiently.
Audio Book
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Keystroke Operator (K)
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This operator represents the act of pressing a key or button on a keyboard, mouse, or other input device.
Examples: Typing a character (e.g., 'a', 'Z', '7'), pressing a modifier key (e.g., Shift, Ctrl, Alt), pressing the Enter key, hitting the spacebar, or clicking a mouse button (distinct from mouse movement).
Typical Time (Highly Variable): The duration of a keystroke is crucially dependent on the user's typing skill.
Very Fast (Expert Typist): Approximately 0.08 seconds.
Average Typist: Approximately 0.20 seconds.
Worst Typist / Unfamiliar Keyboard / Hunting-and-Pecking: Can range up to 1.20 seconds.
For general calculations and unless specified, a commonly used average value for a non-typist or system designer estimating basic interaction is often around 0.28 seconds. This variability underscores the importance of knowing your target user group.
Detailed Explanation
The Keystroke Operator (K) in KLM quantifies the action of pressing keys on a keyboard or buttons on a mouse. This operator is crucial in determining how long it takes a user to input text or commands into a system. Different users will have different keystroke durations based on their typing proficiency, highlighting that a highly skilled typist can press keys much faster than someone who is unfamiliar with the keyboard. Typically, for an expert typist, the time taken is about 0.08 seconds per keystroke, while an average user might take around 0.20 seconds. Understanding user typing speeds is essential for making accurate performance predictions.
Examples & Analogies
Imagine a writing competition where typists of various skill levels are tasked with typing a paragraph. An expert typist, akin to a pianist who knows their keys, can finish the paragraph in just a snap (0.08 seconds per key), whereas a beginner might take considerably longer with each typed character, much like someone who is learning to play an instrument. This difference in keystroke time represents a significant factor when designers create interfaces that require text input.
Pointing Operator (P)
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This operator encapsulates the act of moving a pointing device (most commonly a mouse, but also trackpads, touchpads, joysticks, or light pens) to acquire a specific target on the display screen.
Typical Time: 1.1 seconds (This is an average value derived from empirical studies and attempts to cover typical distances and target sizes. While Fitts' Law provides a more precise model for pointing time, KLM uses a simplified constant for aggregate analysis). This duration implicitly includes the very brief time taken to select the target once the pointer reaches it.
Detailed Explanation
The Pointing Operator (P) measures the time it takes for a user to move their cursor to a specific target on the screen, such as a button or a link. Averaged out, this movement is estimated to take about 1.1 seconds, accounting for both the time to move the cursor and select the target. This operator underscores the importance of target size and distance; larger targets or those placed closer to the user reduce pointing time, making it a crucial consideration in interface design.
Examples & Analogies
Think of playing a video game where you need to click on moving targets. If the targets are large and close together, you can hit them quickly, just like hitting a soccer ball into a wide goal from a short distance. However, if the targets are tiny and far apart, it takes much longer to hit each one, much like trying to kick a ball into a small net at the other end of a field. This illustrates how interface designers need to consider target size and placement in their designs.
Homing Operator (H)
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This operator represents the physical movement of the user's hand between different input devices.
Examples: Moving a hand from the keyboard to the mouse, or from the mouse back to the keyboard, or shifting from a standard keyboard to a numeric keypad.
Typical Time: 0.4 seconds. This operator accounts for the overhead of repositioning the hand across distinct input zones.
Detailed Explanation
The Homing Operator (H) captures the time taken for a user to shift their hand from one input device to another, such as from the keyboard to the mouse. This shift is not instantaneous and is typically estimated to take about 0.4 seconds. Understanding this operator is critical, especially in environments where users frequently switch between different input devices, as it can add considerable time to overall task completion.
Examples & Analogies
Imagine you're a chef in a kitchen, darting between different cooking stations. If you need to move from chopping vegetables on a cutting board (keyboard) to stirring a pot on the stove (mouse), it takes time to reach across your workspace. The hand movement creates a delay in your cooking. Similarly, in a computer context, the time it takes to move your hand from the keyboard to the mouse affects how quickly you can execute tasks.
Drawing Operator (D)
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This operator specifically models the time taken to draw a series of straight-line segments using a pointing device. It's less common in general GUI analysis but relevant for graphic design applications.
Typical Time: 0.9n + 0.16 seconds, where 'n' represents the number of straight-line segments drawn. This formula acknowledges that drawing involves a fixed setup time plus time per segment.
Detailed Explanation
The Drawing Operator (D) is used to measure the time it takes to draw lines with a pointing device, which is particularly relevant for design applications. The time is calculated using a formula that accounts for both a fixed time to initiate drawing and then an additional time based on the number of lines drawn. This operator is vital for tasks involving graphics or drawing that require precise control and timing.
Examples & Analogies
Think of an artist painting a landscape. First, they need a moment to prepare their brush and canvas (the fixed setup time), and then with every stroke they make, it takes additional time for each line they draw. In the context of software, this is similar to a designer using software to create a graphic, where each stroke requires both preparation and execution time.
Mental Preparation Operator (M)
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This is the most abstract and often the most challenging operator to accurately place. It represents the time a user spends engaged in internal cognitive processes such as thinking, recalling information, formulating a plan, making a decision, or scanning for relevant information.
Typical Time: 1.35 seconds (This is a heavily averaged value, as actual mental processes can vary widely. It aggregates various cognitive efforts). Its placement is governed by specific heuristics (discussed in the next lecture).
Detailed Explanation
The Mental Preparation Operator (M) reflects the time users need to think or decide before taking action. This operator is challenging to quantify because it varies greatly from person to person. On average, mental preparation takes about 1.35 seconds. This operator emphasizes that not all delays in task execution come from physical actions; significant time can be spent in thought and planning before an action is taken.
Examples & Analogies
Imagine preparing for a big test. Before you write any answers, you need to stop and think about what you know and plan your responsesβhow to organize your thoughts (the mental preparation time). Similarly, when using software, before you can take a digital action, itβs essential to think about what you want to do, which can take just as long, if not longer, depending on the complexity of the task.
System Response Operator (R)
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This operator represents the time taken by the interactive system to respond to a user's action. It covers computational delays, network latency, screen redraw times, or any other non-human-controlled delay.
Typical Time: This duration is highly context-dependent and must be measured or precisely estimated for the specific system and task being analyzed. It is external to human action and varies significantly.
Detailed Explanation
The System Response Operator (R) accounts for the time it takes for a system to react to a user's action, such as clicking a button or completing a command. This response time can vary greatly based on the system's performance, network speed, and other factors. Accurately estimating this time is essential for a comprehensive analysis of the overall task time, as delays here can significantly impact user experience.
Examples & Analogies
Think of waiting for a friend to respond to a text message. The time you spend waiting isnβt your doing, but it affects how long it takes for you to continue the conversation. In a software context, similar waits occur when a user clicks a button and must wait for the system to process that action and give feedback.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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K (Keystroke): Represents the act of pressing a key, with variable timing based on skill.
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P (Pointing): The movement of a device to select targets, typically taking about 1.1 seconds.
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H (Homing): The time for hand movement between devices, usually about 0.4 seconds.
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M (Mental Preparation): Time for cognitive processes, averaging around 1.35 seconds.
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R (System Response): The asynchronous time taken by the system to register user actions.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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An expert user typing a document can use the Keystroke operator significantly faster than a novice, showing the value of KLM in predicting different user efficiencies.
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When User A points to a button on a screen while User B types a string of text, we can see how the different operators (P vs. K) yield varying interaction times.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
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K for keys, P for point, M for mind, R for response, keep them aligned!
π Fascinating Stories
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Imagine a user in a race. They type quickly (K), point to selections confidently (P), think carefully (M), and wait for system feedback (R). Each action is a part of their journey to victory.
π§ Other Memory Gems
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Remember KPMPR - Keystroke, Pointing, Mental, Preparation, Response.
π― Super Acronyms
KPMR, short for Keystroke, Pointing, Mental Preparation, and Response helps remember the fundamental operators.
Flash Cards
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Glossary of Terms
Review the Definitions for terms.
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Term: Operator
Definition:
A basic action in the Keystroke-Level Model representing distinct user or system actions.
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Term: Keystroke
Definition:
The act of pressing a key or button on an input device.
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Term: Pointing
Definition:
The action of moving a pointing device to select a target on the screen.
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Term: Homing
Definition:
The physical movement of the user's hand between different input devices.
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Term: Mental Preparation
Definition:
The time spent on cognitive processes such as thinking, recalling, or planning.
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Term: System Response
Definition:
The time taken by the interactive system to respond to a user's action.