Pie diagram / charts:These are so-called because the entire graph looks like a pie and its components represent slices cut from a pie. The total angle at the centre of a circle is equal to 360° and it represents the total frequency. It is divided into different sectors corresponding to the frequencies of the variables in the distribution. Eg: Distribution of dental disease in 30-40 yr olds. The segments are then shaded with different shades or colors and an index is provided for these shade colors. However, this diagram cannot be used to represent two or more data sets.