Do we REALLY need to interpolate? If the question asks for say a probability that a normal random variable is greater than so and so for example, is interpolation really necessary, because it seriously makes hardly any difference For example if we want P(Z<1.62) is it really necessary to interpolate between values of .95353 and .95449? It's going to make a difference of .001?
It depends on the question and the marks it carries. For example if there is a 3 mark question asking you to find a probability using the normal distribution, then I would interpolate and find an answer 3 s.f. atleast. On the other hand if the question is about say hypothesis testing then I wouldnt bother interpolating. This is just my opinion.
