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INTERPRETATIONWhat is the meaning of ? •The appropriate interpretation of a confidence interval (for example on ) is: The observed interval [11.9385.87
MARGIN OF ERROR
MARGIN OF ERRORError and margin of errorIn using to estimate the error must be less than or equal to with confidence 100(1-)Error in estimating with . xxXxE)/(*2/nzBnzxl/2nzxu/2
CALCULATING SAMPLE SIZEThe sample size to establish a confidence interval of the form with confidence coefficient is given by EXAMPLEThe yield of a chemical process is being studied. From previous experience yield is known to be normally distributed and σ = 3. The past five days of plant operation have resulted in the following percent yields: 91.6, 88.75, 90.8, 89.95, and 91.3. Based on this information, we want to determine how many more samples must be taken to ensure that the estimate is to be within 1 percent of the true average, with 95% CI?