Scales of Measurement
Scale 
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 Questions
eg. 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 Variables
IV 
• 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 ANOVA
Basic 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 Theories
Health 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 Questions
Weak questions are untestable and broad
Stronger questions are more testable, but less generalizable
Step 4: Define Trials
Estimate 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 Processes
Attention 
Perception 
Memory 
Learning 
Reading, speaking & listening 
Problemsolving, planning, reasoning & decisionmaking 
Attention
Selecting 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 
Perception
How 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 
Memory
Stages 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 Principles
Uncertainty 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 Models
5 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.


Statistics
We 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 Theorem
As 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 ttest
Small 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 Heuristics
Affects 
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 Change
Abstract & Reflective 
Unobtrusive 
Public 
Aesthetic 
Positive 
Controllable 
Trending/Historical 
Comprehensive 
Nielsen Heuristics
Visibility 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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