02-2 Task Analysis.pdf

Task Analysis Assoc Prof. Jeannie S. Lee Task Analysis The study of the way people perform their jobs and achieve their intended goals Aim is to determine What they do What things they use What they must know Helps to better understand user needs, identify tasks the application mus...

Task Analysis Assoc Prof. Jeannie S. Lee Task Analysis The study of the way people perform their jobs and achieve their intended goals Aim is to determine What they do What things they use What they must know Helps to better understand user needs, identify tasks the application must support, or re-define content scope INF2002 Task Analysis Task analysis gathers both declarative and procedural knowledge Declarative: objects and relationships Procedural: task sequences, goals and subgoals Also dependencies and constraints Emphasizes users+existing tasks, rather than desired system as in systems analysis Emphasizes observable behavior and whole job, rather than internal mental state and “unit” tasks as in cognitive models INF2002 Purpose of Task Analysis What your users’ goals are; what they are trying to achieve What users actually do to achieve those goals What experiences (personal, social, and cultural) users bring to the tasks How users are influenced by their physical environment How users’ previous knowledge and experience influence: How they think about their work The workflow they follow to perform their tasks INF2002 Example Task: Cleaning Home INF2002 Example Task: Cleaning Home To clean the home get the vacuum cleaner out fix the appropriate attachments clean the rooms when the dust bag gets full, empty it put the vacuum cleaner and tools away Must know about vacuum cleaners, their attachments, dust bags, cupboards, rooms.. INF2002 Gathering Data for Task Analysis Use various appropriate methods and techniques Observation Interviews Focus groups Collect unstructured lists of words and actions Organize the tasks and subtasks, plus other related information Use notation or diagrams INF2002 Task Analysis Approaches Task decomposition splitting task into (ordered) subtasks Knowledge-based techniques what the user knows about the task and how it is organized Entity/object based analysis relationships between objects, actions and the people who perform them (not covered in detail here) INF2002 Task Decomposition Aims describe the actions people do structure them within task subtask hierarchy describe order of subtasks Most common method Hierarchical Task Analysis (HTA) Decomposing a high-level task into subtasks INF2002 Textual HTA: Cleaning home Hierarchy Description 0. clean the house 1. get the vacuum cleaner out 2. get the appropriate attachment 3. clean the rooms 3.1 clean the living room 3.2 clean the kitchen 3.3 clean the bedrooms 4. empty the dust bag 5. put vacuum cleaner and attachments away Plans Plan 0: do 1, 2, 3, 5 in order; when dust bag full, do 4 Plan 3: do 3.1, 3.2, 3.3 in any order, as needed INF2002 Generating the hierarchy 1. get list of tasks 2. group tasks into higher level tasks 3. decompose lowest level tasks further Stopping rules How do we know when to stop? Is “empty the dust bag” simple enough? Purpose: expand only relevant tasks Motor actions: lowest sensible level INF2002 Make a cup of tea INF2002 Diagrammatic HTA: Make cup of tea INF2002 Refined HTA for making tea How to check or improve the initial HTA? Some heuristics are: paired actions where is “turn on gas”? restructure generate task “make pot” balance is “pour tea” simpler than “make pot”? generalize make one cup... or more INF2002 Refined HTA for making tea INF2002 Knowledge-Based Analyses Aim to understand knowledge required for a task provide training material, how-to manuals take advantage of common knowledge across tasks Focus on objects used in the task actions performed Use taxonomies: to represent levels of abstraction organization (grouping) depends on purpose INF2002 Car Control Taxonomy INF2002 Car Control Taxonomy motor controls steering steering wheel, indicators engine/speed direct ignition, accelerator, foot brake gearing clutch, gear stick lights external headlights, hazard lights internal cabin light wash/wipe wipers front wipers, rear wipers washers front washers, rear washers heating temperature control, air direction, fan, rear screen heater parking hand brake, door lock entertainment numerous! system INF2002 Task Descriptive Hierarchy (TDH) Task Analysis for Knowledge Description (TAKD) TAKD uses three types of branches in TDH taxonomies: XOR — object in exactly one branch AND — object must be in both OR — can be in one, many or none INF2002 Task Descriptive Hierarchy (TDH) motor controls wash/wipe AND function XOR wipers front wipers, rear wipers washers front washers, rear washers position XOR front front wipers, front washers rear rear wipers, rear washers INF2002 Task Descriptive Hierarchy (TDH) Example kitchen item AND /____shape XOR / |____dished mixing bowl, casserole, saucepan, / | soup bowl, glass / |____flat plate, chopping board, frying pan /____function OR {____preparation mixing bowl, plate, chopping board {____cooking frying pan, casserole, saucepan {____dining XOR |____for food plate, soup bowl, casserole |____for drink glass N.B. ‘/|{’ used for branch types INF2002 Entity-Relationship Techniques Focus on objects, actions and their relationships Emphasis on domain understanding not implementation Includes non-computer entities Covered in database design (not here) Example: gardener digs soil using spade INF2002 Entity-Relationship Example Firm: ‘Vera's Veggies’ – a market gardening firm owner/manager: Vera Bradshaw employees: Sam Gummage and Tony Peagreen tools: various tools including a tractor `Fergie‘ two fields and a glasshouse new computer-controlled irrigation system INF2002 Summary Task analysis is the study of the way people perform their jobs Many different approaches Task decomposition Knowledge based analysis Entity/object based analysis INF2002 Summary Determine the data needed to describe current task(s) Gather data using various appropriate methods and techniques Represent the tasks and subtasks, plus other related information Use this data to improve the design INF2002 References Dix et al, Human-Computer Interaction (3rd Edition), Chapter 15 JoAnn T. Hackos and Janice C. Redish, User and Task Analysis for Interface Design INF2002 Hierarchical Task Analysis Activity Conduct a hierarchical task analysis for buying a drink from the vending machine INF2002