**Contribute your data in the front**- Pick up handout and your previous lab sheet
- Open Blackboard and download SPSS instructions
- Slides at http://statr.me/courses.html

- Mean
- Take the average

- Median
- Sort the data from smallest to largest
- If n is odd, median is the center observation
- If n is even, median is the mean of the two center observations

- Quartiles
- Sort the data from smallest to largest, and find the median
- The first quartile Q1 is the median of data to the left of median
- The third quartile Q3 is the median of data to the right of median
- Calculate quartiles by hand, not SPSS

- Skewness
- Skewed left: Long
**Tail**on the left - Skewed right: Long
**Tail**on the right

- Skewed left: Long
- Modes
- Unimodal: One major peak
- Multimodal: More than one peaks

- Interquartile range
- IQR = Q3 - Q1

- Suspected outlier
- < Q1 - 1.5 * IQR,
**OR** - > Q3 + 1.5 * IQR

- < Q1 - 1.5 * IQR,

- Five-number summary
- Skewed distribution, or with outliers

- Mean and standard deviation
- Symmetric, free of outliers