The document discusses measures of central tendency including the mean, median, and mode for ungrouped data sets. The mean is the average and is calculated by adding all values in the data set and dividing by the number of values. The median is the middle number when data is arranged in order. For even data sets, the median is the average of the two middle numbers. The mode is the number that occurs most frequently in the data set. Sometimes there are multiple modes or no mode. The range is the difference between the highest and lowest values in the data set.