An inexperienced analyst determines the average molar mass of a fatty acid sample by titration with aqueous NaOH using phenolphthalein indicator. Instead of stopping the titration when a light pink color is seen, the analyst titrates to a much darker magenta color. This will cause the calculated molar mass to be:

Overshooting the end point will cause error in the calculation of the average molar mass of a fatty acid.

Explanation:

End point can be defined as the point during a titration  process that indicates that the quantity of reactant required to complete a reaction has already been added to a solution. This implies no further titrant need to be added.

Overshooting this end point indicated by the appearance of a much darker magenta color means that the amount of reactant is more than what is required to complete the reaction and therefore the intention of getting the average molar mass of a fatty acid sample will be flawed.