UIUC ECON 203 - Confidence Interval Estimation (2 pages)

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ECON 203 1st Edition Lecture 3 Outline of Last Lecture I Review of key class features 1 Office Hours 2 Homework II Aplia Homework 2 1 Hypothesis Testing Example 12 i Relevant Point Estimate ii Value of Test Statistic iii P value iv Type I error conclusion I Outline of Current Lecture I Office Hours II Confidence Interval Estimation 1 Formulas i Standard Error ii Margin of Error iii Formula Sheet 2 Example on slide 26 of notes package 3 Example on slide 29 of notes package 4 Rounding 5 Example on slide 33 of notes package Current Lecture I Office Hours Monday through Thursday from 11am to 6pm TA s are there ready to help II Confidence Interval Estimation Point estimates include u standard deviation s p etc 1 Formulas i Standard Error for Population Mean w Sigma known standard dev square root of n Population mean w Sigma unknown s square root of n Population Proportion square root of p 1 p n 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 ii Margin of Error For Population Mean w Sigma known z or standard dev square root of n iii Get used to using the formula sheet in the back of the notes package so that when we have an exam you will be used to referring to that sheet 2 Example on slide 26 of notes package Answer 1 a 90 a 10 a 2 05 95 1 a 95 a 05 a 2 025 Z 025 1 96 3 Example on slide 29 of notes package Answer n 70 s 24 000 average 856 000 standard dev 28 000 10 significance level 850000 861000 4 Rounding Always round n up e g calculate 84 2 up to 85 5 Example on slide 33 of notes package Answer n 49 standard deviation 78 average 32 6 It s a z distributing because the standard deviation is known 95 confidence interval 32 6 1 96 78 square root of 49 32 3816 32 8184 99 confidence interval 32 6 2 58 78 square root of 49 32 3125 32 8875