Single-use Promo Codes

Usability, Best Practices & RecommendationsDouglas Cuffman, Information Architect, EBT Team

March 2, 2012

04/10/232

Summary Assignment

Look into any research around accuracy of completion rates for entering character strings at multiple lengths

Requirements

LL Bean catalogs will require a total of 190MM active single-use promo codes in Fiscal 2012. During Peak Season, the requirement will be as much as 76MM in a given week in Dec Wk2.

Problem

Usability Issues: Promotional codes are difficult to use and even impossible to use if poorly constructed.

Findings

To date no usability research studies seem to have been published specifically on the topic of promo codes and completion rates. However, a significant amount of research has been published on cognitive numerical limits and human ability to process data sets within the spectrum of short-term memory.

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Related Research Findings “The Magic Number”

According to cognitive psychologist George A. Miller , in one of most-cited articles in psychology, “"The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information”, “The number of objects an average human can hold in working memory is 7 ± 2.”

However, recent research has demonstrated that the correct number is probably around three or four.

Permutations, Combinations and “Chunking”

It is also worth noting that this “magical number” pertains to both permutations and combinations and is therefore not restricted to a static set of three or four single digits.

For example, “The quick brown fox jumps over the lazy dog” is 35 permutations of the English alphabet and nine combinations, or “chunks”. At nine chunks this set is rather difficult to process, but “The quick brown fox jumps” is only five chunks, lessening cognitive load.

Adding personalized meaningfulness and significance enhances usability, as comprehension increases from producing a “cognate set”.

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Recommended Best PracticesUsability of Codes, Passwords, Numbers, and Letters

Avoid letters and numbers that may cause confusion, such as the lower case ‘l’ (L) and the number ‘1', the upper case ‘O’ and the number ‘0', or the number ‘8’ and the upper case ‘B’.

If specific letters or numbers are required, use the case of the letter that is easily distinguished. For example, you may choose to use a lower case ‘d’ instead of an upper case ‘D’ because the upper case ‘D’ can sometimes be confused with the upper case ‘O’ or the number ‘0'.

If possible, always present the number zero as ‘Ø’ instead of an ‘0' to avoid confusion.

Utilizing the “dyslexia font” can help avoid both poor readability and confusion, not just for customers who suffer from Dyslexia, but for anyone using a promo code.

Designing a promo code that can easily be read aloud within two seconds will typically remain in the temporary memory for a maximum of twenty seconds and will allow users to focus on typing while viewing the screen, rather than glancing back and forth from the printed asset to the screen, increasing the possibility of input error.

Designing meaningfulness into a promo code can aid in usability and faster completion rates. “Meaningfulness” refers to utilizing cognitive hooks. For example:

street address + first name + name of marketing campaign

“2382 Timothy Spring Hunting Sale”

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Do the Math

Permutations and Combinations

Doing a quick calculation, using 26 items and 5 chunks, gives us a total of 45,239,040 combinations.  We can increase that total if we add numerals to the 26 alpha item or eliminate similar-looking items from the set and add more numerals, for example.

Adding numerals, increasing the set to 36 permutations and 6 combinations, produces a net total of 1,947,792 possible single-use promo codes.

Formula :Permutation: nPr = n! / (n-r)! Combination: nCr = nPr / r! 

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Recommendations

Limit promo code to managable length, based upon best practices

Contruct promo code using meaningful cognates

Utilize an algorithm to generate high yield of unique codes

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Wrap-up, Q & A, Questions

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SourcesWikipedia“The Magical Number Seven, Plus or Minus Two” http://en.wikipedia.org/wiki/The_Magical_Number_Seven,_Plus_or_Minus_Two

Dr. Jacob Nielson“Short-Term Memory and Web Usability” http://www.useit.com/alertbox/short-term-memory.html

Katie Mauck“Usability of Codes, Passwords, Numbers, and Letters” http://www.usabilitysciences.com/usability-of-codes-passwords-numbers-and-letters

Thomas Baekdal“The Usability of Passwords”http://www.baekdal.com/insights/password-security-usability

Lyle Mullican“The Problem with Passwords”http://www.alistapart.com/articles/the-problem-with-passwords/

Cognitive Hooks Blog“Cognitive Hooks”http://cognitivehooks.wordpress.com/about/

YouTube“Dyslexie is a typeface for dyslectics.”http://www.youtube.com/watch?v=VLtYFcHx7ec

EasyCalculation.com“Permutation, Combination – Calculator”http://easycalculation.com/statistics/permutation-combination.php

Single-use Promo CodesUsability, Best Practices & Recommendations