Designing usable number entry interfaces

Number Entry InterfacesSarah Wiseman !UCL Interaction Centre

Why Number Entry?

• Errors are important!

• Happens every day!

• So many interface options!

• Numbers are wicked cool

Mars Climate Orbiter

Mars Climate Orbiter

• Determine distribution of water on Mars!

• Monitor daily weather conditions!

• Determine temperature of atmosphere!

• Look for evidence of climate change

Mars Climate Orbiter

• Determine distribution of water on Mars!

• Monitor daily weather conditions!

• Determine temperature of atmosphere - REALLY HOT!

• Look for evidence of climate change

Mars Climate Orbiter

Lesson: !

Remember that numbers sometimes mean something - not just random strings

Number Entry in the !Medical Domain

Errors with Infusion Pumps

Errors in Design

12 !

Errors with Numbers compared to Text

Number Entry in the !Medical Domain

Lesson: !

Remember that errors in number entry can have serious consequences.

Humans checking for number errors

Horse Cow

Shepe Donkey

Humans checking for number errors

Horse Cow

Shepe Donkey

1111 1804 2911 3417

Humans checking for number errors

Lesson: !

Number errors are really, really hard to spot

The design of the keypad

The Pushbutton phone

The Pushbutton phone cord

Making Number Entry Better

UCD in Number entry

• “I checked the user is able to press the button ok”

UCD in Number entry

• “I checked the user is able to press the button ok”!

• What numbers does the user actually want to enter?

Benford’s Law

Blood Pressure Terminal Digit

Perc

enta

ge o

f occ

urre

nce

0

20

40

60

80

Terminating digit

0 5 Even Number Odd number (not 5)

Digits in the hospital

0 1 2 3 4 5 6 7 8 9 .

Digit

Frequency

0500

1000

1500

2000

2500

Numbers in the hospitalVolume Frequency (%)

100 29.87

1000 9.97

50 9.07

500 6.36

20 3.81

Adapting interfaces

Optician’s Interface Design

Applying this to design

Faster Slower

Possible future design

Tailoring interfaces for numbers

Lesson: !

Match the interface to the task it is being used for, make the common numbers easy

Learning from text entry

Words and non-wordsLast night the Great British Bake Off was shocking

British was night Great shocking Last Off the Bake

Proum flim shoyar larof quask tullep exuge serah

Rteu fgdwww weqk sreemg wkgj gfmss mnoaish

little bit faster than

faster than

faster than

Effect of words versus !non words

Faster

Larger look-ahead

Larger copy span

I think the editors need to answer for their actions

Testing text entry interfaces

Testing number entry interfaces

“We generated a set of random numbers and asked users to enter them using the interface”

Similarity to numbers?

Pony ≠ Prfw !

1066 ≠ 9379

Results of Familiarity In

terk

eypr

ess

inte

rval

ms

200

250

300

350

400

Familiar Non Familiar

Words Numbers

Test with Realistic Numbers

Lesson: !

You wouldn’t test text entry with random strings, don’t test number entry with them

Number Entry - !Points to think about

• Number mean something, they aren’t just shapes!

• Number errors are big problem, and they are hard to spot!

• Think about how your interface could be tailored, keypad isn’t the only way!

• Don’t treat random numbers as though they are representative - familiarity matters

Thanks, go and do really good number entry stuff!

@oopsohno

www.swiseman.co.uk

• Deininger, R. L. (1960). Human factors engineering studies of the design and use of pushbutton telephone sets. Bell System Technical Journal, 39, 995–1012. !

• Retrieved fromhttp://www.vcalc.net/touchtone_hf.pdf