[AccessD] Reference Material

Mitsules, Mark S. (Newport News) Mark.Mitsules at ngc.com
Wed Aug 25 10:17:40 CDT 2004


Jim,

Well thank you for pointing out my obvious limitations;)  I have a sneaking
suspicion that a mathematician may indeed be needed before this is all said
and done.  I will have to keep that in mind so that I can bring in
assistance sooner rather than later.


Mark



-----Original Message-----
From: Jim Hewson [mailto:JHewson at karta.com] 
Sent: Wednesday, August 25, 2004 10:42 AM
To: Access Developers discussion and problem solving
Subject: RE: [AccessD] Reference Material



Mark,
We have a contract to do an analysis of the probability of detection (POD)
of inspectors.
The inspectors would "inspect" specimens similar to aircraft parts (e.g.
lugs).
All the data for the specimens, inspectors and inspections (including
equipment used) is stored in an Access database.  Statistical analysis is
done to determine the POD.
When developing the database we looked for reference material to help with
the statistical analysis in Access.  We did not find any. We purchased the
"FMS Total Access Statistics" to help the analysis.  Our mathematician
didn't like it.  We also felt it created a lot of overhead that wasn't
needed.
Bottom-line.  We rolled our own.  Statistical formulas can be broken down
into their components. Then queries are created to "populate" the formula.
For example, the Chi-square analysis to determine the "Coefficient of
Contingency" (our mathematician's words) uses one query that calculates the
components.  The sequence of events for the calculations begins with a
select query that uses eight tables and a form for the criteria.  That query
is used in another select query using six tables (some are repeated).  Using
the previous query, another query does some calculations. And the final
query is created using the previous query to do more calculations.  
The final query results is the components of the formula.  The formula is
placed in the text box of the report. 
The formula is:
=Sqr((1/([C1]*[R1])*(([A]-([C1]*[R1]/[N]))*([A]-([C1]*[R1]/[N]))))+(1/([C2]*
[R1])*(([B]-([C2]*[R1]/[N]))*([B]-([C2]*[R1]/[N]))))+(1/([C1]*[R2])*(([C]-([
C1]*[R2]/[N]))*([C]-([C1]*[R2]/[N]))))+(1/([C2]*[R2])*(([D]-([C2]*[R2]/[N]))
*([D]-([C2]*[R2]/[N]))))) 

For our purposes this works.  

My suggestion is to take it step by step, slowly.  
Have a mathematician involved that can calculate the correct answer manually
on your sample data.  Determine the data you need to do the calculations and
analyze the data collection process.  Determine if you are actually
collecting the correct data for the statistical analysis.  At every step
when creating the queries, determine if the results are correct.  I found it
was best to work backwards.  Look at the formula and determine where each
component should come from the data.  After all the queries, criteria, etc.
have been created compare the results with the mathematicians answer - do
they match?  If not, go back and find out why.  If so, CELEBRATE!  You've
earned it.  

Triple - no - quadruple the time you think it might take to do this.  Each
formula could take up to a week or more to perfect.  Access will do the
calculations, but be prepared to add user interface feedback.  One report
that has several sub reports that have numerous calculations (using many
queries) has taken several minutes to finish.

HTH

Best of luck.

Jim



-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com]On Behalf Of Mitsules, Mark
S. (Newport News)
Sent: Wednesday, August 25, 2004 8:14 AM
To: [AccessD]
Subject: [AccessD] Reference Material


Group,

Can anyone suggest some reference material that discusses developing
sophisticated Access reports which will include statistical analysis and
graphing?


Mark
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