Remaining 10.1 Objectives State in nontechnical language what is meant by a “level C confidence interval” Explain what it means by the “upper p critical value” of the standard Normal distribution For a known population standard deviation (that is mu) construct a level C confidence interval for a population mean.

List the 4 necessary steps in the creation of a confidence interval (see Inference Toolbox). Identify three ways to make the margin of error smaller when constructing a confidence interval. Once a confidence interval has been constructed for a population value, interpret the interval in the context of the problem.

Determine the sample size necessary to construct a level C confidence interval for a population mean with a specified margin of error. Identify as man y of the six “warnings about constructing confidence intervals as you can. (For example, a nice formula cannot correct bad data.)

! Be sure to check that these conditions for constructing a confidence interval for mu are satisfied before you perform any calculations. Read and work through Example 10.4

These are the most commonly used z* values. Confidence level Tail area Z* 90% 0.05 1.645 95% 0.025 1.960 99% 0.005 2.576 These are the most commonly used z* values.

2nd, VARS or DISTR Remember that 0<C<1

Form of a confidence interval (Estimate)  (margin of error) (Estimate)  (critical value of t or z)  (standard error)

From Example 10.5

Inference Toolbox (p 631) Step 1: Parameter Step 2: Conditions (see also p 627) Step 3: Calculations Step 4: Interpretation

PRACTICE: TPS 10.7, 10.9, 10.11, 10.12

How CI’s behave  

Caution There are numerous cautions on p 636 & 637… READ THEM

PRACTICE TPS 10.15 through 10.18 Cooperative assessment 10.1 NOTE: Calculating confidence interval is only part of the inference process. Follow the steps in the Inference Toolbox (p 631).