Ch 10Presentation of Data — Class 11 Economics, concept-first.

Data gathered from surveys, censuses or records are usually voluminous — so bulky, scattered and disorganised that they cannot be understood as they stand.

In textual presentation the data are described inside the running text itself, as part of the paragraph.

In tabular presentation the data are arranged in rows (read horizontally) and columns (read vertically), so that any figure can be located at once by the row and column it sits in.

Qualitative classification groups data according to attributes — qualities or characteristics that cannot be measured in numbers, such as sex, social status, physical status, religion or nationality.

Quantitative classification groups data by a characteristic that can be measured numerically — for example age, height, income or production.

Temporal classification uses time as the classifying variable, so the data are grouped according to when they occur. The time unit may be an hour, a day, a week, a month or a year.

Spatial classification groups data according to place — the location to which each figure belongs. The place may be a village or town, a block, a district, a state or a country.

A good statistical table is built from several standard parts; when these are put together systematically they form the table.

The table number is given to a table so that it can be identified, and so that one table can be distinguished from another when several are presented together.

The title of a table narrates what the table is about — it tells the reader, in a few words, the contents and coverage of the data displayed.

At the top of each column in a table, a short column designation is given to explain what the figures in that column stand for. This heading is called the caption or column heading.

A stub, also called a row heading, is the label given to each row of a table, just as a caption labels each column.

The body of the table is its main part — it holds the actual data. Every figure in the body has a fixed location determined jointly by the row and the column it lies in.

The unit of measurement states the units in which the figures of the table are expressed, and it should always be given along with the title.

The source is a brief statement, placed at the bottom of the table, that tells the reader where the data came from. It lends credibility and lets the reader trace or verify the figures.

The note is the last part of a table. It explains any special feature of the data that is not self-explanatory and has not already been made clear elsewhere in the table.

Diagrammatic presentation is the third way of showing data, and it gives the quickest understanding of a situation compared with textual or tabular forms.

A geometric diagram presents data through simple geometric shapes. Two types fall under this heading:

A bar diagram is a set of equispaced, equal-width rectangular bars, one bar for each class or category of data.

A simple bar diagram shows a single set of values using one bar per category, the height of each bar equal to the value it represents.

A multiple bar diagram is used to compare two or more sets of data side by side. For each category, a group of adjacent bars is drawn, one bar for each data set, and the groups are separated from one…

A component bar diagram (also called a sub-diagram) shows each bar divided into parts, so that the reader sees both the total and the sizes of the components that make it up, and can study the relatio…

A pie diagram (or pie chart) is a component diagram in the shape of a circle whose area is divided among the components in proportion to their sizes.

A frequency diagram is used to picture data that are in the form of a grouped frequency distribution. Four such diagrams are in common use:

A histogram is a two-dimensional diagram made of rectangles: the base of each rectangle is a class interval (marked between class boundaries on the X-axis) and its area is proportional to the class fr…

A frequency polygon is a plane figure bounded by straight lines — an alternative to the histogram, and in fact derived from it.

A frequency curve is a graphic representation of a frequency distribution obtained by drawing a smooth, free-hand curve through the points of a frequency polygon.

An ogive, also called the cumulative frequency curve, plots cumulative frequencies (instead of simple frequencies) along the y-axis against the class limits.

An arithmetic line graph, also called a time-series graph, plots time (hour, day, week, month, year, etc.) along the x-axis and the value of the variable along the y-axis, then joins the plotted point…

This chapter has shown that data can be presented in three forms — textual, tabular and diagrammatic — and that the right choice depends on the data.

Key points of the chapter: