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.NH
Experience with Students.
.PP
.I
Learn
.R
has been installed on
many different 
.UX
systems.
Most of the usage is on the first two scripts, so these
are more thoroughly debugged and polished.
As a (random) sample of user experience,
the
.I learn
program has been used at Bell Labs at Indian Hill
for 10,500 lessons in a four month period.
About 3600 of these are in the files script,
4100 in the editor,
and 1400 in advanced files.
The passing rate is about 80%,
that is, about 4 lessons are passed for every one
failed.
There have been 86 distinct users of the files script,
and 58 of the editor.
On our system at Murray Hill, there have been nearly 2000 lessons
over two weeks that include
Christmas and New Year.
Users have ranged in age from six up.
.PP
It is difficult to characterize typical sessions with the
scripts;
many instances exist of someone doing one or two lessons
and then logging out, as do instances of someone pausing
in a script for twenty minutes or more.
In the earlier version of
.I learn ,
the average session in the files course took 32 minutes and covered
23 lessons.
The distribution is quite
broad and skewed, however; the longest session was
130 minutes and there were five sessions shorter than
five minutes.
The average lesson took about 80 seconds.
These numbers are roughly typical for non-programmers;
a
.UX
expert can do the scripts at approximately 30 seconds
per lesson, most of which is the system printing.
.PP
At present working through a section of the middle of the files
script took about 1.4 seconds of processor time per lesson,
and a system expert typing quickly took 15 seconds of real time per lesson.
A novice would probably take at least a minute.
Thus a UNIX system could support ten students working simultaneously
with some spare capacity.
