The Frequency Table
The frequency table in which data are arranged or grouped into conveniently established numerically ordered classes or categories.
The frequency of a value is the number of times it appears in the distribution. In Constructing a frequency table, attention must be given to:
- Number of Classes: The number of classes should not be less than five and not more than fifteen.
- Class Interval and Class Width: The class interval refers to the length of the interval of a particular class, which class width refers to the size of the class.
- Class Limits and Class Boundaries: The midpoint of any class is the average of the two limits or boundaries of the affected class.
- Class marks or midpoints: The midpoint of any class is the average of the two limits or boundaries of the affected class.
Inclusive and Exclusive Class Intervals
Inclusive class intervals usually have values equal to the upper and lower limits included in them, while the exclusive class intervals have values to the upper and lower class limits not included in it.
Graphical Representation of Data
Statistical data can be represented using charts and graphs. The choice depends on the nature of the data on hand.
All the same, it is usual to represent discrete data using charts as, bar and pie charts which are particularly suited for categorical (or quantitative) series.
A bar chart consists of a series of rectangular bars, drawn either vertically or horizontally for each with the height of each bar is proportional to the magnitude of its frequency.
A pie chart is a circular diagram cut into segments with the size of each segment being proportional to the size of the category it represents.
Since there are 360 degrees in the circle, each category, therefore, takes its appropriate share of the total.