Averages and spread
Groups
Averages and range from a list
The three averages and the range of a raw list, and which one to trust.
Averages from frequency tables
The mean, median, mode and range read or calculated from a frequency table.
Averages from grouped data
The modal class, median class and estimated mean once the raw values are gone.
Quartiles and the interquartile range
The Higher-tier measures of spread: quartiles and the range of the middle half.