ISEN-ASTC-L is a service of the Association of Science-Technology Centers
Incorporated, a worldwide network of science museums and related institutions.
*****************************************************************************

Regarding sample size for formative evaluation, here's an interesting
argument for from the field of Web usabiliy testing:

Jakob Nielsen's Alertbox, March 19, 2000:
Why You Only Need to Test With 5 Users
http://useit.com/alertbox/20000319.html
"Elaborate usability tests are a waste of resources. The best results come
from testing no more than 5 users and running as many small tests as you can
afford."

The explanation depends on viewing usability/formative testing as discovering
uasability problems and includes a mathematical formula that demonstrates the
deminishing returns/decreasing numbers of problems discovered as the number
of user tests increases.

Eric Gyllenhaal
Selinda Research Associates

In a message dated 9/3/2004 11:30:14 PM Central Daylight Time,
[log in to unmask] writes:

> ------------------------------
>
> Date:   Fri, 3 Sep 2004 10:09:43 -0500
> From:   =?iso-8859-1?Q?P=E9rez_Castellanos_Leticia?=
>      <[log in to unmask]>
> Subject: Formative evaluation
>
> ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> Incorporated, a worldwide network of science museums and related
> institutions.
> *****************************************************************************
>
>
> I'm currently working in a new interactive museum in Mexico City, we =
> just started the process of evaluate some exhibits in the design and =
> production phase (formative). I'm having problems to explain why this =
> kind of evaluation does not need large statistical samples, great part =
> of the team thinks that we need to have representatives samples and, I =
> read in some classical texts (Screven, Griggs, Hein) that this is not =
> necessary nor practical.
>
> Does any one have a good methodological frame to pick good samples for =
> this kind of evaluation? Or does any one could recommend me the =
> "Formative evaluation handbook"? I prefer things I can consult through =
> web because in Mexico is difficult to get those books, although we can =
> buy some basic and interesting texts.
>
> Thanks in advance
>
> Leticia Prez Castellanos
> Research and Evalaution Area
> Espacio Cultural y Educativo Betlemitas
>
> ***********************************************************************


***********************************************************************
More information about the Informal Science Education Network and the
Association of Science-Technology Centers may be found at http://www.astc.org.
To remove your e-mail address from the ISEN-ASTC-L list, send the
message  SIGNOFF ISEN-ASTC-L in the BODY of a message to
[log in to unmask]