Pairw ise Variability Index: Variability Index: Pairw ise - - PowerPoint PPT Presentation

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Pairw ise Variability Index: Variability Index: Pairw ise - - PowerPoint PPT Presentation

Dec 24, 2023 220 likes •398 views

Pairw ise Variability Index: Variability Index: Pairw ise Evaluating the Cognitive Evaluating the Cognitive Difficulty of Using Mobile Text Difficulty of Using Mobile Text Entry Systems Entry Systems Frode Eika SANDNES Frode Eika SANDNES

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SLIDE 1

Pairw ise Pairw ise Variability Index: Variability Index: Evaluating the Cognitive Evaluating the Cognitive Difficulty of Using Mobile Text Difficulty of Using Mobile Text Entry Systems Entry Systems

Frode Eika SANDNES Frode Eika SANDNES

Faculty of Engineering Faculty of Engineering Oslo Oslo University University College, Oslo, College, Oslo, Norw ay Norw ay

Hua Hua -

  • Li JIAN

Li JIAN

Faculty of Faculty of Arts Arts National Cheng National Cheng Kung Kung University University, , Tainan Tainan, Taiw an , Taiw an

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SLIDE 2

Evaluating Evaluating mobile mobile text entry text entry

  • Performance oriented

Performance oriented

– – Inter keystroke delays Inter keystroke delays – – Characters Characters per per second second/ /minute minute – – KSPC ( KSPC (keystrokes keystrokes per per characters characters) ) – – … …

  • Error oriented

Error oriented

– – Error Error rate rate – – … …

  • Cognitive

Cognitive

– – NASA TLX ( NASA TLX (task load index task load index ) ) – – … …

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SLIDE 3

Cognitive processing Cognitive processing and and typing rhythm typing rhythm

  • Some relationship betw een typing

Some relationship betw een typing speed, speed, error error rate and rate and cognitive difficulty of typing cognitive difficulty of typing task task

  • Duration of inter

Duration of inter-

  • keystroke delay related

keystroke delay related to to cognitive processing cognitive processing load load

  • Regular typing rythm

Regular typing rythm -

  • >

> cognitively cognitively balanced text entry strategy balanced text entry strategy

  • Use

Use median median based measures based measures to to avoid avoid

  • utliers
  • utliers –

– thought w onders thought w onders and and resting resting breaks breaks

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SLIDE 4

The pairw ise variability index The pairw ise variability index

i i i i i

d d d d pvi + − =

+ + 1 1

The difference betw een tw o consecutive timestamps di = bi+1 – bi Select the median of all the pvii values

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SLIDE 5

Experiment Experiment

  • Subjects

Subjects: :

– – 3 3 volunteer volunteer undergraduate undergraduate students at OUC students at OUC

  • Equipment

Equipment : :

– – Desktop Desktop computer computer w ith w ith full full keyboard keyboard, , monitor, monitor, mouse mouse

  • 5

5-

  • keys pammed

keys pammed to to keys keys a, s, d, f and [ a, s, d, f and [space space] ]

– – Text entry implemented Text entry implemented as as apples apples, , running running in in brow ser brow ser

  • Procedure

Procedure for for each method each method

– – 5 5 minutes practice minutes practice – – 15 15 minutes typing session minutes typing session ( (source text source text

  • n
  • n screen)

screen) – – questionnaire questionnaire

  • Measurements

Measurements

– – Timestamped keystroke events Timestamped keystroke events

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SLIDE 6

3 3 multi multi-

  • keystroke

keystroke strategies strategies

  • Multitap

Multitap ( (similar similar to old to old handsets) handsets)

  • Tree

Tree -

  • based

based

  • One

One -

  • stroke (

stroke (similar similar to T9) to T9)

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SLIDE 7

3 3 multi multi-

  • keystroke

keystroke strategies strategies

  • Multitap

Multitap ( (similar similar to old to old handsets) handsets)

  • Tree

Tree -

  • based

based

  • One

One -

  • stroke (

stroke (similar similar to T9) to T9)

Key-1: a, b, c, d, e, f Key-2: g, h, i, j, k, l Key-3: m, n, o, p, q, r Key-4: s, t, u, v, w , x, y, z Key-5: [break-key] Characters retreived by repeadedly pressing the key labelled w ith the desired character until it appear, then the break key.

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SLIDE 8

3 3 multi multi-

  • keystroke

keystroke strategies strategies

  • Multitap

Multitap ( (similar similar to old to old handsets) handsets)

  • Tree

Tree -

  • based

based

  • One

One -

  • stroke (

stroke (similar similar to T9) to T9)

Step 1: Chose category Key-1: a, b, c, d, e Key-2: f, g, h, i, j Key-3: k, l, m, n, o Key-4: p-q, r, s, t, u, Key-5: v, w , x, y-z, [ ] Step 2: Chose w ithin cat. Key-1: a Key-2: b Key-3: c Key-4: d Key-5: e

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SLIDE 9

3 3 multi multi-

  • keystroke

keystroke strategies strategies

  • Multitap

Multitap ( (similar similar to old to old handsets) handsets)

  • Tree

Tree -

  • based

based

  • One

One -

  • stroke (

stroke (similar similar to T9) to T9)

Key-1: a, b, d, e Key-2: f, g, h, i, j ,k, l, m Key-3: n, o, p, q, r Key-4: s, t, u, v, w , x, y, z Key-5: [space] Key w ith desired character once. Word appear after w ord completed– or resolve ambiguities

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SLIDE 10

Results Results

26.2 7.7 26.5 Mean ch/min 31.1 18.6 27.2 Mean ch/min 0.41 0.55 0.29 Median npvi 3/5 0/5 4/5 Preverence 0.46 0.49 0.39 Median npvi 0.55 2.13 0.24 Median ikd Subject 3 4/5 5/5 1/5 Preverence 0.32 0.46 0.25 Median npvi 1.94 1.02 0.52 Median ikd Subject 2 4/5 0/5 3/5 Preverence 28.5 13.0 22.5 Mean ch/min 1.2 1.4 0.5 Median ikd Subject 1 One-stroke Tree-based MultiTap measure Subject

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SLIDE 11

Results Results

26.2 7.7 26.5 Mean ch/min 31.1 18.6 27.2 Mean ch/min 0.41 0.55 0.29 Median npvi 3/5 0/5 4/5 Preverence 0.46 0.49 0.39 Median npvi 0.55 2.13 0.24 Median ikd Subject 3 4/5 5/5 1/5 Preverence 0.32 0.46 0.25 Median npvi 1.94 1.02 0.52 Median ikd Subject 2 4/5 0/5 3/5 Preverence 28.5 13.0 22.5 Mean ch/min 1.2 1.4 0.5 Median ikd Subject 1 One-stroke Tree-based MultiTap measure Subject

The tree based method is the slow est method, the least popular and the one w ith the largest npvi value

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SLIDE 12

Results Results

26.2 7.7 26.5 Mean ch/min 31.1 18.6 27.2 Mean ch/min 0.41 0.55 0.29 Median npvi 3/5 0/5 4/5 Preverence 0.46 0.49 0.39 Median npvi 0.55 2.13 0.24 Median ikd Subject 3 4/5 5/5 1/5 Preverence 0.32 0.46 0.25 Median npvi 1.94 1.02 0.52 Median ikd Subject 2 4/5 0/5 3/5 Preverence 28.5 13.0 22.5 Mean ch/min 1.2 1.4 0.5 Median ikd Subject 1 One-stroke Tree-based MultiTap measure Subject

The one-stroke method is the fastest to use and therefore prefered by subects, but the high npvi value indicate cognitive difficulty

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SLIDE 13

Results Results

26.2 7.7 26.5 Mean ch/min 31.1 18.6 27.2 Mean ch/min 0.41 0.55 0.29 Median npvi 3/5 0/5 4/5 Preverence 0.46 0.49 0.39 Median npvi 0.55 2.13 0.24 Median ikd Subject 3 4/5 5/5 1/5 Preverence 0.32 0.46 0.25 Median npvi 1.94 1.02 0.52 Median ikd Subject 2 4/5 0/5 3/5 Preverence 28.5 13.0 22.5 Mean ch/min 1.2 1.4 0.5 Median ikd Subject 1 One-stroke Tree-based MultiTap measure Subject

The MultiTap method is easy to use and has the low est npvi value indicating cognitive

  • ease. But is is slow er

to use than one-stroke

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SLIDE 14

Conclusions Conclusions – – median median npvi npvi

  • Useful

Useful measure measure for for comparing various comparing various text entry strategies text entry strategies

  • Gives

Gives an an indication of cognitive indication of cognitive difficulty difficulty

  • Can

Can be be applied directly applied directly to to keystroke keystroke logs logs, independent , independent of strategy

  • f strategy
  • No

No normalisation normalisation or

  • r scaling necessary

scaling necessary

  • Easy

Easy to to compute compute

  • Roboust

Roboust to to outliers

  • utliers
  • Should

Should not be not be used exclusively used exclusively, , but but in in conjunction w ith other quantities conjunction w ith other quantities

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SLIDE 15

Thank Thank you you!!! !!!

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