re: How accurate is a home appraisal for the mortgage company?

I’ve sold 5 houses over the last 20 years, my experience has been pretty much what TigerDebaiter mentioned. The appraiser has always been selected and sent by the loan company that was providing the buyers loan, the loan company wants the business and has already agreed to make the buyer a loan, so they select appraisers that they are familiar with and know will being them back whatever appraisal the contract needs.
The appraiser wants to keep getting called often by the loan company so they make their appraisal match what the lender wants. One house I sold, the appraiser never pulled out any type measuring device, only spent about 6 mins inside and outside the house, sent the lender an appraisal $2000 above my contract price.
Last home I sold, I was asking about $15,000 more than I thought I could get, the appraiser did about a 20 min look around, sent lender an appraisal $11,000 more than I was asking, at closing I saw that the young buyers had qualified for some kind of special loan program and were getting $10,000 above contract for their loan amount, then I understood why there was an $11,000 unexpectedly high appraisal. So to sum it up, they can make it whatever they want to and can come up with comps to make it work.