1) Define the following terms.
a) Class interval
The difference between the upper limit and the lower limit of a class is called the class interval.
b) Open-ended class
A class with no upper limit is called an open- ended class.
c) Frequency distribution
A tabular presentation of nominal or ordinal data as classes along with the frequency of their occurrence is called frequency distribution.

2) What are the factors one should keep in mind while preparing a frequency distribution for continuous data?
While preparing frequency distribution we should be keep in mind: number of class intervals, their width and whether they have to be closed or open.


Bar Diagram : It is often defined as a set of thick lines corresponding to various values of the variable. It is different from histogram where width of the rectangle is important.
Class and Class Limits : It is a decided group of magnitudes having two ends called class limits or class boundaries.
Class Range : Also called class interval is the difference of two  limits of a class. It is equal to upper limit minus lower limit. It is also called class width.
Continuous Frequency : A continuous frequency distribution in formed Distribution where the variable can take any value between two numbers like height and weight, income, temperatures, etc.
Exclusive Type Class : A class interval which includes all observations Interval that are greater than or equal to the lower limit but less than the upper limit.
Frequency Polygon : It is a broken line graph to represent a frequency distribution and can be obtained either from a histogram or directly from the distribution.
Frequency Curve : It is a smoothened graph of a frequency distribution obtained from frequency polygon through free hand tracing in such a way that the area under both of them is approximately the same.
Inclusive Type Class : A class interval in which all observations lying Interval between and including the class limits are included.
Discrete Frequency : A discrete distribution or discrete series is formed Distribution where the variable can take only discrete values like 1,2,3,..... Number of children in a family, number of students in a university, etc. are examples of discrete variable.
Open-end Class : A class in which one of the limits is not specified. Mid-value : It is the average value of two class limits. It falls just in the middle of a class.
Relative Frequency : It is frequency distribution where the frequency of  Distribution each value is expressed as a fraction or a percentage of the total number of observations.
Histogram : It is a set of adjacent rectangles presented vertically with areas proportional to the frequencies.
Simple and Sub-divided Bar : In the case of simple bar diagram only one diagram variable can be presented. A sub-divided bar diagram is used to show various components of a phenomenon.
Pie Chart : It is a circle sub-divided into components to present proportion of different constituent parts of a total. It is also called pie chart.
Source:IGNOU Study Material