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Lecture Comments (3)

1 answer

Last reply by: Vojislav Mitrovic
Wed May 7, 2014 7:27 AM

Post by Vojislav Mitrovic on May 7, 2014

Could you please help with context meaning of the margin of error(ME)?

For example, by doing several examples I realized that whenever I have a task about estimating sample size for certain confidence interval it often says that ''They would like the estimate to be WITHIN 0.0X (some percent, such as 0.04, 0.03,etc.) of the true proportion/mean with a XX% confidence level.
However, I came across come task where it said ''with a WIDTH of at most 0.08'' and in the answer the width was divided by 2, and then they got the ME=0.04.

Therefore, could you please tell why are we dividing WIDTH by 2 in order to get ME so that we could estimate desirable sample size for certain confidence interval ?  

Here is the complete task i got:

A student organization at a university is interested in estimating the proportion of student in favor of showing movies biweekly instead of monthly. How many students should be sampled to get a 90 percent confidence interval with a width of at most 0.08?

I am thankful in advance for your time and help.

Vojislav Mitrovic

0 answers

Post by John Haddad on March 11, 2012

Excellent explanation - much better than my prof who just delved into CIs without explaining estimation in general. Thanks.

Introduction to Estimation

  • An estimator is the sample statistic used to estimate a population parameter. The estimate is the value assigned to a parameter based on the value of the statistic.

  • A point estimate is the value of the statistic.

  • An interval estimate is the point estimate plus or minus some margin of error.

Introduction to Estimation

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Estimation 0:06
    • Parameter
    • Estimate
    • Estimator
    • Example
  • Steps for Estimation 2:21
    • Example: Dartboard
    • Consistent/Bias
    • Inconsistent/Unbiased
    • Consistent/Unbiased
  • Point Estimate 5:33
    • Example
  • Interval Estimate 6:35
    • Margin of Error
  • Confidence Interval 7:35
    • Confidence Level
  • Example 8:10
  • More on Confidence Intervals 10:18
    • Confidence Level Increase
    • Sample Size Increase