select not using index

We have a select statement: "select count(*), avg(responseTime) from atable where seId = 1" Even though we have an index on seId it will not use it, even after an update statistics and 80,000 rows. If we change the where to 'where seid between 1 and 1' it uses the index. If we just do a 'select count(*)' it uses the index. (seId is an integer). I seem to remember a long while ago some similar problems with Informix, but do not remember the details - does anyone else have any idea why this would not use the index. We use Online 7.13 on a DEC Alpha using OSF 3.2d. Any help appreciated. Paul R. (75052.1341@compuserve.com)