stddev_pop, stddev_samp strange behaviour

Hi,

I've created a test table with some random data and try to execute stddev_pop _samp, and var_pop _samp as below.

select stddev_pop(value),stddev_samp(value) from test
select var_pop(value),var_samp(value) from test

I noticed that stddev_pop return same value as stddev_samp, and var_pop return same value as var_samp. I have
PostgreSQL8.2.4 and asume something is wrong. The data I used should return different value for each function. 

MZ