Charles Arthur is absolutely right: you’ve heard a song and like it and think “shall I buy the album”. If the song is the first one on the album, the album is rubbish. If the song is somewhere else, the album is likely to be OK. Think Muse:Absolution, where Sing for Absolution is the fourth tuen for example. Think U2:How to Dismantle… where Vertigo is the first song and there is only one other good one on the album.