Presentation of Data

After data are collected and organised, they must be presented in a clear, attractive way so that readers can understand them at a glance. The simplest form is tabular presentation — arranging data in rows and columns in a statistical table.

A good table is far easier to read than a paragraph full of figures. A well-made statistical table has these parts:

• Table number — for easy reference.
• Title — states clearly what the table shows (what, where, when).
• Head note — extra information below the title, e.g. the unit ("in ₹ crore").
• Captions — the headings of the columns (vertical).
• Stubs — the headings of the rows (horizontal).
• Body — the main part containing the actual figures (the data).
• Footnote — explains anything special about an entry.
• Source note — states where the data came from (important for trust).

A simple example table:

Here "Boys/Girls" are captions, "Science/Commerce" are stubs, and the numbers form the body.

Diagrams turn numbers into pictures that even a non-expert can grasp instantly. Diagrammatic presentation shows data as bars, rectangles or circles. The most common types:

• Simple bar diagram — a set of equal-width bars whose heights show the values. The taller the bar, the larger the value.
• Multiple bar diagram — two or more bars are drawn side by side for each category, to compare them (e.g. boys vs girls in each stream).
• Component (sub-divided) bar diagram — each bar is divided into parts to show the components that make up the total.
• Pie chart (circle diagram) — a circle divided into slices, where each slice's angle is proportional to its share. Since the whole circle is 360°, the angle of a slice = (component ÷ total) × 360°.

A simple bar diagram of the example data looks like this:

When data are in class intervals (a frequency distribution), we present them as graphs rather than bar diagrams. The main graphs are:

• Histogram — a set of adjoining rectangles (no gaps between them), where the width of each rectangle is the class interval and the height is the frequency. It looks like a bar chart but the bars touch, because the classes are continuous.
• Frequency polygon — a line graph formed by joining the mid-points of the tops of the histogram bars with straight lines.
• Frequency curve — a smooth, free-hand curve through those mid-points.
• Ogive (cumulative frequency curve) — a graph of the cumulative frequencies. The "less than" ogive rises from left to right; the "more than" ogive falls. The point where the two ogives cross gives the median.

A separate, important graph is the time series (line) graph — used when data are recorded over time (e.g. yearly GDP). Time is taken on the horizontal axis and the value on the vertical axis, and the points are joined to show the trend (rising, falling or fluctuating) over the period.

A simple histogram of the marks frequency distribution (0–10:2, 10–20:4, 20–30:5, 30–40:5, 40–50:4) looks like this — notice the rectangles touch: