Calendar

May 22

Knowing (by) Designing 2013

May 27

13th Intl. Conf. on New Interfaces for Musical Expression

May 28

Graphics Interface 2013

May 21

“ Computer analyst to programmer: "You start coding. I'll go find out what they want." ”

-- Popular computer one-liner

Share this quote on...
Get more quotes via RSS or by joining our Usability Quote of the Day Facebook Page

Featured chapter

Read the fascinating history of Wearable Computing, told by its father, Steve Mann

Read Steve's chapter !

Help us help you!

Spread the word:
Donate
Other ways to help

Keoun Nah

Update pic

Add description

← Button will not work: You have not enabled Javascript. How do I enable it?

Rename / change spelling

Add publication

← Button will not work: You have not enabled Javascript. How do I enable it?

Publications by Keoun Nah (bibliography)

1995

Edit | Del

Kreifeldt, John G. and Nah, Keoun (1995): Adding and Subtracting Percentiles -- How Bad Can It Be?. In: Proceedings of the Human Factors and Ergonomics Society 39th Annual Meeting 1995. pp. 301-305.

“When performing anthropometric analysis or design, it frequently happens that some particular anthropometric value is not tabulated although it would appear to be derivable by adding or subtracting two relevant and tabulated dimensions. Because percentile values are usually required, there is the temptation to add or subtract the relevant percentile values of the two tabulated dimensions. In some cases, this will produce minimal or no error between the actual percentile value and the result of adding/subtracting the tabulated values, while in other cases, the resulting percentile will be very seriously in error. The magnitude of the errors depends on the percentiles, correlation coefficient and ratio of the standard deviations of the two variates. This paper details the combinations of these three factors for which adding/subtracting two identical percentile values produces acceptable as well as grossly misleading results. Several tables, charts and equations are provided to aid in this common problem. The results may be particularly useful when only the ratio of standard deviations may be known or approximated rather than their individual values. In general, subtracting percentiles leads to greater errors than adding them.”

Add publication