Point Estimation. For a population of size N, a simple random sample is a sample selected such that each possible sample of size n has the same probability of being selected. There are two types of estimates: point and interval. Expert Judgment The best place to get project estimating data is from a technical subject matter expert. The approach essentially correlates cost and manpower information with parameters describing the item to be costed. A sampling distribution is a probability distribution for a sample statistic. There are several types of parameter estimates: Point estimates are the single, most likely value of a parameter. INTRODUCTION: Estimation Theory is a procedure of “guessing” properties of the population from which data are collected. In these cases, the statistics can't be used since the sample hasn't been taken yet. estimating (guessing) θ on the basis of having observed X = x. Unbiased estimators An estimator θˆ= t(x) is said to be unbiased for a function θ if it equals θ in expectation: E For example, $a<\bar{x}