Scales of MeasurementScale  Description  Examples  Nominal  Catergorical; order doesn't matter  Gender: 1 (male), 2 (female)  Ordinal  Ordered values. Order matters, but not difference between values  Agreement: 1 (SD), 2 (D), 3 (Neutral), 4 (A), 5 (SA). Pain Scale (110)  Interval  Numeric. Difference between values is meaningful  Relative Temperature: °C, °F, pH  Ratio  Numeric. Zero and ratios are meaningful  Height, Weight, Absolute Temperature (K) 
Measurement is the process of observing and recording the observations collected as a part of a research effort.
Step 1: Define Research Questionseg. How does your technique...  • Compare with alternative techniques?  Techniques  • For which target population?  Target users  • For what tasks?  Tasks  • In terms of what measures?  Performance measures  • In what context?  Other factors 
Target users: need to be specific  students who have been using the desired medium consistently, for example
Performance measures: like speed, accuracy
Other factors: other than different techniques, what factors can influence the measures?
Step 2: Define VariablesIV  • Factors manipulated in the experiment • Have multiple levels  DV  • Factors being measured  Control variables  • Attributes fixed throughout the experiment • Confounders  attributes that vary and aren't accounted for  Random variables  • Attributes that are randomly sampled • Increases generalisability 
Confounders rather than IVs could have caused changes in DV.
They make it difficult/impossible to draw conclusions.
Order of presentation and prior experience are two important confounders that we need to control. (by counterbalancing and proper sampling)
Step 3: Arranging Conditions (WithinSubjects)List the IV and their levels  eg. Technique (2 levels: Gesture, Marking) Menu depth (2 levels: 1, 2)  Determine counterbalancing strategies for each IV  • Full counterbalancing (n! conditions) • Latin Square (n conditions) • No counterbalancing (sequential) (1 condition)  Determine minimum no. of participants  Multiply all conditions together  Determine factorial arrangement of conditions  Put the permutations together  Determine arrangement for each participant 
Condition reduction strategies:
• Pick the most important/interesting factors to test
• Run a few IVs at a time  if strong effect, include IV in future studies, otherwise, pick fixed control value for it
Oneway ANOVABasic Idea: ANOVA tries to find the sources of this variance:  • due to difference between groups • Variability within each group  Total Variability = BetweenGroup + WithinGroup  𝑆𝑆^{𝑇}=𝑆𝑆^{𝑀}+𝑆𝑆^{𝑅}  Ratio of Variability  F = (𝑆𝑆^{𝑀}/DF^{B}) / (𝑆𝑆^{𝑅}/DF^{W})  If the experiment is successful, then 𝑆𝑆^{𝑀}>𝑆𝑆^{𝑅}. Betweengroup variability will explain more variance than withingroup.  The bigger the F value, the smaller the p value, and the less like the null hypothesis (no difference) is true.  Steps:  1. Calculate 𝑆𝑆^{𝑇}  𝑆𝑆^{𝑇}=𝑠_𝑔𝑟𝑎𝑛𝑑^{2} (𝑁−1) DF^{T} = (N1)  2. Calculate 𝑆𝑆^{𝑀}  𝑆𝑆^{𝑀}=∑_i𝑛_𝑖 (𝑥 ̅_𝑖−𝑥 ̅_𝑔𝑟𝑎𝑛𝑑 )^{2} • sum of n difference of means from the grand mean DF^{M} = (No. of groups  1)  3. Calculate 𝑆𝑆^{𝑅}  𝑆𝑆^{𝑅}=∑_𝑖𝑠_𝑖^{2} (𝑛_𝑖−1) • sum of varianceno. of results in each group DF^{R} = total no. of results  no. of groups  Double check: 𝑆𝑆^{𝑇}=𝑆𝑆^{𝑀}+𝑆𝑆^{𝑅} & DF^{T} = DF^{M}  DF^{R}  4. Calculate Mean Squared Error  MS^{M} = SS^{M}/DF^{M} MS^{R} = SS^{R}/DF^{R}  5. Calculate Fratio  F = MS^{M} / MS^{R}  if F is lower than value in Ftable, then p < 0.05 results are statistically significant 
Behaviour TheoriesHealth Belief Model  Perceived Benefits v Perceived Barriers, Perceived Theat, SelfEfficacy, Cues to Action all contribute to Likelihood of Engaging in HealthPromoting Behaviour  Theory of Reasoned Action  Selfbelief + Influenced beliefs, Attitudes, Intention Behaviour  SelfDetermination Theory  Intrinsic (selfbenefit) v Extrinsic motivation (external benefits)  Goal Setting Theory  Basic idea: goal serves as a motivator, work harder as long as they believe goal is achievable. Importance in Clarity, Challenge and Feedback  Social Cognitive Theory  Cognitive, Environmental and Behavioural factors determine human behaviour  Fogg Behavioural Model  Behaviour = Motivators, Ability, Triggers • Motivators: Sensation, Anticipation, Social Cohesion • Ability: Train or Simplify • Triggers: Spark, Signal or Facilitator 
  Testable Research QuestionsWeak questions are untestable and broad
Stronger questions are more testable, but less generalizable
Step 4: Define TrialsEstimate the time for each trial  around 510 seconds?  Estimate the time for each condition  Time for each trial no. of trials for each condition  Balance the trials (so experiment is within 45 min)  Combine with the condition arrangement  Essentially, find the total time the experiment will take 
Trials: a single repetition of a single condition
Typically want to have at least 3 trials per condition to increase reliability
Consider time: trials should last for 45 minutes (excluding pre and post interviews)
Cognition ProcessesAttention  Perception  Memory  Learning  Reading, speaking & listening  Problemsolving, planning, reasoning & decisionmaking 
AttentionSelecting things to concentrate on at a point in time from the mass of stimuli around us  Focus on information that's relevant to what we are doing  Involves audio/visual senses  Design implications:  • Make information salient if it needs attending to • make things stand out •avoid cluttering interface 
PerceptionHow information is acquired from the world, and transformed into experiences  Design representations that are readily perceivable  Implication:  • Group information • Text should bne legible and distinguishable from the background 
MemoryStages of memory:  • Encoding • Storage • Retrieval  Encoding:  • Determines which info is attended to in environment + how it's intepreted • Context affects extent to which info can be retrieved  different context difficult to recall  Implications:  • Focus attention/no complicated procedures • Recognition over recall • Provide various ways of encoding and retrieving info (searching v history)  Storage:  Sensory Memory:  • shortestterm memory, acts like a buffer for stimuli retrieved • Ability to remember and process info at same time • Information will decay within 1015s • Extended by rehearsal, hindered by interference  Longterm Memory:  •Declarative Memory (factual info): • Semantic Memory (general) + Episodic Memory (personal knowledge) • Procedural Memory (skills/habits)  Retrieval:  • Internal/External stimuli for retrieval cues • Encoded at same time as memory 
Cognitive System PrinciplesUncertainty Principle  𝑇=𝐼^{𝐶}𝐻  where T = Decision time, H = log2(n+1) (where n is the no. of choices)  Variable Rate Principle  More effort Faster processing (ie. cycle time  Cycle time also diminishes with practice: 𝑇_𝑛=𝑇_1 𝑛^{−𝛼}  Fitts' Law  𝑇_𝑀=𝑎+𝑏 log_2(𝐴/𝑊+1)  where A = distance to target, W = error tolerance 
Transtheoretical Models5 Stages of Change  Precontemplation, Contemplation, Preparation, Action, Maintenance  Processes of Change  Consciousness raising, Social liberation, Goal setting, Helping relationships, Rewards 
Processes of change can be applied to 5 stages of change.
Each person will value different processes differently.
  StatisticsWe use sample statistics to estimate/make inferences about population parameters  Due to uncertainty and variability, conclusions and estimates may not always be correct.  Need measures of reliability  • Confidence interval  • the confidence that the true population value of a parameter falls within a confidence interval • affected by: variation & sample size  • Level of significance  •“P value”, α • the prob. of rejecting the null hypothesis when it is actually true (Type I error) • ie. concluding that there is a difference when there may be no actual difference • signifies the probability that the difference is due to chance  Level of Significance Thresholds  • Not significant (p>.1; p=n.s.) • Marginally significant (p<0.1) • (Fairly) significant (p<.05) • (Good) significant (p<.01) • (Excellently) significant (p<.001) 
Central Limit TheoremAs the sample size gets larger...  The mean of sample means approaches the population mean  The standard error of the sameple means = the standard deviation of the population mean  𝑆𝐸=𝑠/√𝑛=√(𝑉𝑎𝑟𝑖𝑎𝑛𝑐𝑒/𝑛) 
2Sample ttestSmall sample sizes not normal distribution  Use tdistribution  Steps:  1. Calculate mean difference 2. Calculate SD 3. Calculate no. of SDs away from 0 4. Calculate df = smaller n  1 5. Calculate pvalue, for significance (which pvalue is it closest to)  If given desired confidence interval, steps:  1. Given desired CI 2. Get no. of SDs away from 0 from ttable 3. Calculate margin of error in units ((2) SD)  Difference between groups more likely to be significant if:  • Large difference between means • Small SD or large n in each group  Assumptions:  • Continuous variable • Independent samples 
Also called the independentsamples ttest
Other tests:
• Onesample ttest (sample v constant)
• Pairedsampled ttest (withinsubjects, repeated measures)
• Oneway ANOVA
Cognitive HeuristicsAffects  where emotions influence decisions  Availability  where people overestimate the importance of information available to them  Confirmation Bias  where we only listen to information that confirms out preconceptions  Halo Effect  where an outcome in one area is due to factors from another  Framing Effect  where the words used push listeners in a certain direction 
Implications: watch out for biasing your participants.
Structural Equation Modeling
Design Strategies for Lifestyle Behaviour ChangeAbstract & Reflective  Unobtrusive  Public  Aesthetic  Positive  Controllable  Trending/Historical  Comprehensive 
Nielsen HeuristicsVisibility of system status  Match system and real world  User control and freedom  Consistency and standards  Error prevention  Recognition over recall  Flexibility and efficiency of use  Aesthetic and minimalist design  Help users recognise, diagnose, recover from errors  Help and documentation 

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