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# Reminder

• Contribute your data in the front
• Pick up handout and your previous lab sheet
• Slides at http://statr.me/courses.html

# Important Concepts

• 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

# Important Concepts

• 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

# Important Concepts

• Skewness
• Skewed left: Long Tail on the left
• Skewed right: Long Tail on the right
• Modes
• Unimodal: One major peak
• Multimodal: More than one peaks

# Detecting Outliers

• Interquartile range
• IQR = Q3 - Q1
• Suspected outlier
• < Q1 - 1.5 * IQR, OR
• > Q3 + 1.5 * IQR

# Choosing a Summary

• Five-number summary
• Skewed distribution, or with outliers
• Mean and standard deviation
• Symmetric, free of outliers