"to draw a reliable conclusion" - this is an appropriate phrase for use in formal (legal, scientific) texts.

to draw / reach a reliable conclusion

"evidence on which to base a reliable conclusion"

"it is impossible to draw any reliable conclusions"

Note: the word "conclusions" is quite often in the plural.

This depends on the syntax you want to use. I am simply assuming that you might want to use the noun "conclusion".

There are, of course, other options, with the verb "conclude" + adverb, as the other answerers have indicated.