Fanr 3000 1st Edition Lecture 10 Outline of Last Lecture I Hypothesis Testing II T Tests III Types of T tests Outline of Current Lecture I Determining Sample Size II Calculate Sample Size Current Lecture I II Determining Sample Size Mean variance o Increase samples decrease variance Subject to time budget and ease of selection constraints o Task determine how large of a sample a good estimate of population parameter would require Determine how much error you are willing to accept in estimating the mean of a population o Sample size should be statistically and practically efficient Calculate Sample Size 1 Using the bound on the sampling mean a Based on the absolute amount of error acceptable based on the standard error of the mean b Bx 2Sx 2 Using the standard deviation and desired closeness or coefficient of variation CV and allowable acceptable error AE The formula used varies based on whether or not N in population is known Finite population when N is known o Using BOUND on the sampling mean These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute n number of individuals you will need to sample N number of individuals in your population B your bound typically 2 times your Standard Error but doesn t have to be s your variance As the bound decreases less error willing to accept you have to sample more 1 We need N total of observations in the population 2 We need to determine a desired bound on the population mean 3 We need to estimate the variance expected in the population a Pilot sample b Information from other similar population o Using CV AE When we want to achieve a certain allowable error we can use a similar equation Where CV the coefficient of variation AE allowable error As the allowable error decreases less error willing to accept you have to sample more 1 We need N total of observations in the population 2 We need to determine a desired allowable error on the population mean 3 We need to estimate the CV expected in the population Infinite population when N is unknown o Need to know The standard deviation or the CV The desired objective e g to be within 3 ounces of the true weight of a bird or the allowable error e g 5 error or Where t tn 1 2 and E desired objective o ALWAYS ROUND UP o Practical considerations 1 Cost 2 Trading off allowing error and or confidence is an acceptable procedure