Confidence+Interval

1. Population mean ( µ ) is found by calculating sample mean ( Χ )

2. Z-score is found by first defining a confidence level – usually 95 %, equal to α-value=0.05

3. Then use appendix A in Healey to find corresponding Z-value – 95% confidence level, Z=1.96

4. N is the sample size

5. And population standard deviation ( σ ) we usually don’t know, and therefore use sample standard deviation (s) and N-1 from our sample