**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.

**Keywords**

**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