Well I guess..........
it depends on the purpose of the audit. Since there are a number to choose from, it'd be helpful to know what that was.
Personally, unless you are trying to replicate a 3rd party audit, as in before registration/surveillance, I can't see why you'd (randomly) want to see training records:mg: What are you trying to establish?
Have you had a change in personnel? In such a case you'd be better off finding which specific people haven't had training to perform their assignments.
I'm not surprised that you were challenged on the sampling. I'm thinking the manager was (covertly) challenging the whole purpose of the audit. Using a sampling plan is of no consequence to you and most of all, him. You probably don't have a 'focus' for the audit that management would endorse, so until the planning addresses an issue that they see as value added, the audits will miss vital opportunities.
By way of example; there was a company which always had product quality issues during the summer. They employed local 'interns' to cover for vacation working. Because they chose to audit 'an element a month' (QS-9000 standard), they missed '4.18' every year (one year completely, then by 1 month the next year.....). Shouldn't they have audited the training process when it was implemented to see what was going on?? (i.e. how effective it was).
So, my advice is look at your overall audit scheduling, not the sampling. Don't be random, that's an external audit technique and not for an internal auditor.
Andy