- What's the probability?
- Know observed value
- Z-score -> percentiles

- What's the observed value
- Know probability
- Persentiles -> z-score
- observed = mean + z standard deviation

- Please do your worksheet in groups
- Please get started with your mixable assignment

- Mean height of a grown American men: 1.776m(5ft10in)
- SD: 9.6cm(3.78in)
- Is there any people with negative height?
- z-score of 0? (-18.5)

- How small is it?
- We have 70 billion people in the world now
- We can assume even larger, there are 107.6 people ever lived on earth
- exist one's probability is

- 95% confidence is
- 29 thousand billion billion billion billion billion billion billion billion people!
- How large is it?
- a computer of the current generation, it would need years to count this number.
- Much longer than the age of the earth.

- Essentially, all models are wrong, but some are useful. -- George E. P. Box
- This artile is written by Patrik Perlman, Significance, feb. 2013, 46-48