Question

if a drop of the naoh solution adheres to the side of the erlynmer flask during standardization then how does the error affect the molar concentration

Answer 1

mean the drop of NaOH is not involved in your standard solution u prepared, and will have some other concentration :) may be lesser than what u expected:)

Answer 2

Fewer moles of NaOH would be in solution (assuming this drop stays on the side), thus, the molarity of the solution would be decreased.