- Definition: A 95% confidence interval is an interval calculated from
**sample data**which is guaranteed to capture the true**population parameter**in 95% of all**samples** - Estimate
- Don't know population parameters
- Don't know whether it contains true population parameters

- Conclusions always applied to the
**population**. - Our conclusion about the population is
**never**completely certain. - The
*bigger*the confidence level, the*wider*the confidence interval. - The
*bigger*the sample size, the*narrower*the confidence interval.

- Proportion
- Mean

- : sample proporsion
- : population proporsion
- : sample size
- Confidence Interval:

- : single measurement or everybody in general
- : sample mean
- : population mean
- : sample standard deviation
- Confidence Interval:

- Need a SRS
- Data must be collected correctly(no bias)
- Outliers are BAD
- Sample size should be fairly large

- Please do your worksheet in groups
- Please continue your mixable assignment