What is an unbiased estimator of a population parameter?

• An?estimator?is a?statistic?that is used to estimate a?population parameter
  • When a sample is used with the estimator, the value that it produces is called an?estimate
• An estimator is called?unbiased?if the?expected value?of the estimator is?equal?to the?population parameter
  • An estimate from an unbiased estimator is called an unbiased estimate
  • This means that the?mean?of the?unbiased estimates?will get?closer?to the?population parameter?as more samples are taken

What are the unbiased estimates for the mean and variance of a population?

• If you had the data for a?whole population?you could find the?actual population mean?and?variance?using

Is there an unbiased estimate for the standard deviation?

• Unfortunately square rooting an unbiased variance?does not?result in an unbiased standard deviation
• There is?not a formula?for an unbiased estimate for the?standard deviation?that works for all populations
  • Therefore it is better to just work with the variance and not the standard deviation
• If you need an estimate for the standard deviation then you can use:
  • This won’t be unbiased?but it will be a good estimate

How do I calculate unbiased estimates?