Do sampling methods

How much "error" is too much before you are no longer confident about your estimates or research findings?  Do sampling methods have anything to do with this?  Watch the video below and discuss (8 or more sentences). 

Video

https://www.khanacademy.org/math/ap-statistics/estimating-confidence-ap/one-sample-z-interval-proportion/v/conditions-for-valid-confidence-intervals