Statistics and Hypothesis Testing

Sample Variance, Sample Standard Deviation, Standard
Error
Why
◮ The sample variance and sample standard deviation are
interesting in their own right as a description of the spread in
the data. Is income equally or unequally distributed Do
winters vary from year to year
◮ As we can estimate the population mean using the sample
mean, we can estimate the population variance and standard
deviation using the sample variance and standard deviation.
◮ The sample variance and standard deviation of the underlying
data are needed to estimate the variance and standard
deviation of the sample mean. (We need the latter as a
measure of how precisely the sample mean estimate the
population mean.)