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Interval Estimation

Interval Estimation. 2013/ 12/ 23. Interval estimate. Sample statistic (point estimator) can not be expected to provide the exact value of population parameter. An interval estimate is often computed by adding and subtracting a value, called the margin of error, to the point estimate.

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Interval Estimation

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  1. Interval Estimation 2013/12/23

  2. Interval estimate • Sample statistic (point estimator) can not be expected to provide the exact value of population parameter. • An interval estimate is often computed by adding and subtracting a value, called the margin of error, to the point estimate. • The general form of an interval estimate is point estimate ± margin of error

  3. Sampling distribution of 1 -  of all values /2 /2 interval does not include m  interval includes m interval includes m [------------------------- -------------------------] [------------------------- -------------------------] [------------------------- -------------------------]

  4. Interval estimate of a population mean(s known) • Interval estimate of m: • Lloyd’s example where: is the sample mean 1 - is the confidence coefficient z/2 is the z value providing an area of /2 in the upper tail of the standard normal probability distribution s is the population standard deviation n is the sample size

  5. Interval estimate of a population mean(sunknown) • Interval estimate of m: • Credit card balances example where: 1 - = the confidence coefficient t/2 = the t value providing an area of /2 in the upper tail of a t distribution with n - 1 degrees of freedom s = the sample standard deviation

  6. Interval estimate of a population proportion • Interval estimate of p: • Women golfers example where: 1 - is the confidence coefficient z/2 is the z value providing an area of /2 in the upper tail of the standard normal probability distribution is the sample proportion

  7. Determining the sample size • Sample size for an interval estimate of a population mean: • Sample size for an interval estimate of a population proportion

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