BUSS1020 Lecture Notes - Lecture 8: Standard Deviation, Probability Plot, Sample Size Determination

• School: University of Sydney
• Department: Business Studies
• Course: BUSS1020
• Professor: Erick Li

Document Summary

Confidence interval provides additional information about variability of estimate. How much uncertainty is associated with a point estimate of a population parameter. Interval estimate provides more information about a population parameter than does a point estimate confidence interval. Our confidence that the interval will contain the unknown population parameter (percentage < 100%) Point and interval estimate for mean ( is unknown) If is known, then can also be known (need mean to calculate sd) Student-t distribution (mean = 0, variance = 1) If population sd is unknown, can sub sample sd, s: extra uncertainty s varies in different samples, normally use student-t distribution instead of normal distribution. Assumptions: population sd is unknown, population is normally distributed. If population is not normal, use large sample (clt still works) Interpreting interval requires assumption that clt holds i. e. n is large enough or population distribution is normal. Normality of population can be assessed by: normal probability plot, qqplot, histogram.