Average of logarithms

From: wp_xxyyzz (werner.pamler_at_freenet.de)
Date: 12/25/04 

Date: Sat, 25 Dec 2004 01:40:58 +0100

Hi,

a field of an Access table contains numbers for which I have to
calculate the mean value of their logarithms for various grouping criteria.

The following SELECT query does work (Access 97 and ADO w/Delphi 7):

SELECT
   Avg(Log([TTF])) AS logTTF,
   1/(273+[Temp]) AS InvTemp,
   Log([Current]) AS logJ
FROM ReliabilityData
WHERE
   (((ReliabilityData.TTF) Is Not Null) AND
   ((ReliabilityData.[AG/Full])="full") AND
   ((ReliabilityData.Spacing)=0.5))
GROUP BY
   1/(273+[Temp]), Log([Current]);

However, when I remove the WHERE criteria, the query fails with an error
"Data type mismatch in criteria expression":

SELECT
   Avg(Log([TTF])) AS logTTF,
   1/(273+[Temp]) AS InvTemp,
   Log([Current]) AS logJ
FROM ReliabilityData
GROUP BY
   1/(273+[Temp]), Log([Current]);

Even a simple
   SELECT Avg(Log([TTF]) FROM ReliabilityData
results in the same error.

What am I doing wrong?

Werner