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A Mathematical Model of the Finding of Usability Problems
Why You Only Need to Test with 5 Users
저자 소개
A U

T

H

O

R

Jakob Nielsen has been called:!
• "the king of usability" (Internet Magazine)!
• "the guru of Web page usability" (The New York Times)!
• "the next best thing to a true time machine" (USA Today)!
• "the smartest person on the Web" (ZDNet AnchorDesk)!
• "the world's leading expert on Web usability" (U.S. News
& World Report)
A mathematical model of the finding of usability problems
어떻게 계산했어?
A POISSON MODEL OF THE FINDING
OF USABILITY PROBLEMS

‣ 단위 구간 안에 어떤 사건이 몇 번 발생할 것인지를 표현하는 이산 확률 분포	

‣ 어떤 단위구간(예, 1일)동안 이를 더 짧은 작은 단위의 구간(예 : 1시간)로 나눌 수 있고

이러한 더 짧은 단위구간 중에 어떤 사건이 발생할 확률은 전체 척도 중에서 항상 일정해야 한다.!
‣ 두 개 이상의 사건이 동시에 발생할 확률은 0에 가깝다.!
‣ 어떤 단위구간의 사건의 발생은 다른 단위구간의 발생으로부터 독립적이다.!
‣ 특정 구간에서의 사건 발생확률은 그 구간의 크기에 비례한다.!
‣ 푸아송분포 확률 변수의 기대값과 분산은 모두 λ이다.
A POISSON MODEL OF THE FINDING
OF USABILITY PROBLEMS

‣ 간단하고 이해하기 쉬우며, 개연성있는 포아송 분포를 이용하기 위해,

어떠한 시험에서든 주어진 사용성 문제를 발견할 확률은 이전의 시험과 독립적이라 가정.	

‣ 이런 가정은 전통적인 소프트웨어 개발 프로젝트의

프로그래밍 에러(버그)를 찾는 과정을 설명할 때도 이용해왔다.
A mathematical model of the finding of usability problems
I N T E R FA C E D E B U G G I N G M E T H O D S

‣ 사용자 테스트

: 실제 사용자를 모집하여 그들이 주어진 과업을

해결하기 위해 시스템과 어떻게 인터랙션하는지

관찰하는 방법.


‣ 휴리스틱 평가

: 사용성 전문가들이 정해진 사용성 원칙들을

바탕으로 사용자 인터페이스를 평가하는 방법.
A mathematical model of the finding of usability problems
A mathematical model of the finding of usability problems
왜 5명이 제일 좋아?
A P R I O R I E S T I M AT E S O F T H E O P T I M U M
N U M B E R O F E VA L U AT O R S A N D T E S T
USERS

‣ 비용 대비 효과를 평가하여 몇 명을 기준으로 한 사용성 테스트가 가장 좋은지 알아봄.

이 과정에서, 과거의 경험과 연구 자료를 이용해 어떻게 사용성 테스트의

비용 대비 효과 평가를 할 수 있는지 보여줌.
COSTS

고정비

변동비

사용자 테스트

$3,000

$1,000

휴리스틱 평가

$4,000

$600
BENEFITS

이용자

이익 / 1 사용성 문제

소규모

$1,000

중규모

$15,000

대규모

$200,000
A mathematical model of the finding of usability problems
결론
ITERATIVE DESIGN
UT #1

UT #1

<

UT #2

UT #3
A mathematical model of the finding of usability problems

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A mathematical model of the finding of usability problems

  • 1. A Mathematical Model of the Finding of Usability Problems Why You Only Need to Test with 5 Users
  • 3. A U T H O R Jakob Nielsen has been called:! • "the king of usability" (Internet Magazine)! • "the guru of Web page usability" (The New York Times)! • "the next best thing to a true time machine" (USA Today)! • "the smartest person on the Web" (ZDNet AnchorDesk)! • "the world's leading expert on Web usability" (U.S. News & World Report)
  • 6. A POISSON MODEL OF THE FINDING OF USABILITY PROBLEMS ‣ 단위 구간 안에 어떤 사건이 몇 번 발생할 것인지를 표현하는 이산 확률 분포 ‣ 어떤 단위구간(예, 1일)동안 이를 더 짧은 작은 단위의 구간(예 : 1시간)로 나눌 수 있고
 이러한 더 짧은 단위구간 중에 어떤 사건이 발생할 확률은 전체 척도 중에서 항상 일정해야 한다.! ‣ 두 개 이상의 사건이 동시에 발생할 확률은 0에 가깝다.! ‣ 어떤 단위구간의 사건의 발생은 다른 단위구간의 발생으로부터 독립적이다.! ‣ 특정 구간에서의 사건 발생확률은 그 구간의 크기에 비례한다.! ‣ 푸아송분포 확률 변수의 기대값과 분산은 모두 λ이다.
  • 7. A POISSON MODEL OF THE FINDING OF USABILITY PROBLEMS ‣ 간단하고 이해하기 쉬우며, 개연성있는 포아송 분포를 이용하기 위해,
 어떠한 시험에서든 주어진 사용성 문제를 발견할 확률은 이전의 시험과 독립적이라 가정. ‣ 이런 가정은 전통적인 소프트웨어 개발 프로젝트의
 프로그래밍 에러(버그)를 찾는 과정을 설명할 때도 이용해왔다.
  • 9. I N T E R FA C E D E B U G G I N G M E T H O D S ‣ 사용자 테스트
 : 실제 사용자를 모집하여 그들이 주어진 과업을
 해결하기 위해 시스템과 어떻게 인터랙션하는지
 관찰하는 방법.
 ‣ 휴리스틱 평가
 : 사용성 전문가들이 정해진 사용성 원칙들을
 바탕으로 사용자 인터페이스를 평가하는 방법.
  • 13. A P R I O R I E S T I M AT E S O F T H E O P T I M U M N U M B E R O F E VA L U AT O R S A N D T E S T USERS ‣ 비용 대비 효과를 평가하여 몇 명을 기준으로 한 사용성 테스트가 가장 좋은지 알아봄.
 이 과정에서, 과거의 경험과 연구 자료를 이용해 어떻게 사용성 테스트의
 비용 대비 효과 평가를 할 수 있는지 보여줌.
  • 15. BENEFITS 이용자 이익 / 1 사용성 문제 소규모 $1,000 중규모 $15,000 대규모 $200,000
  • 18. ITERATIVE DESIGN UT #1 UT #1 < UT #2 UT #3