SCI1020 Lecture 9: Part 4a Inference about variables
22 Dec 2018
School
Department
Course
Professor
Document Summary
Inference about population mean or matched pair mean. Problem: unknown means we cannot use the z procedures previously learned. When we do not know the population standard deviation (which is usually the case), the sample standard deviation s. When the standard deviation of a statistic is estimated from data, the result is called t statistic. The standard error of the sample mean, x-bar, is. Extra error is introduced into the procedure, especially for small sample sizes when s c of the population value, . Ws gosset ( student ) in 1908 identified a need to accommodate the extra uncertaint. Student"s t-distribution a broader version of the normal distribution which allowe. The t density curve is similar in shape to the standard normal curve. The spread of the t distributions is a bit greater than that of the standard normal curve slightly fatter in the tails). As n increases, s is a more accurate estimation of .
