Meaning: Arranging raw data systematically through Editing, Classification, and Tabulation.
1. EDITING OF DATA
Meaning: Checking collected data for mistakes to ensure quality.
Check for: Completeness (no missing values), Consistency (same format), Accuracy (correct values), Homogeneity (same type).
2. CLASSIFICATION OF DATA
Meaning: Grouping data based on common features (e.g., students by gender/marks).
Objectives: Present facts simply, Show similarities/differences, Help comparison, Show relationships, Prepare for tabulation.
Good Classification: Clear, Non-overlapping classes, Flexible, Stable, Suitable for enquiry, Arithmetically accurate.
Basis of Classification:
- Chronological: Time (Jan 2022, Feb 2022).
- Geographical: Place (Kerala, Tamil Nadu).
- Quantitative: Numbers (age, marks 0-20, 20-40).
- Qualitative: Qualities (gender, occupation).
STATISTICAL SERIES
Meaning: Classified data arranged in logical order.
Individual Series: Each item listed separately (15, 18, 20, 22).
Discrete Series: Values that can't be divided (number of children).
Continuous Series: Values that can be divided (height ranges 150-160 cm).
FREQUENCY DISTRIBUTION
Meaning: Shows how many times each value occurs in classes.
Elements: Frequency (count), Class Limits (lower & upper), Class Interval (upper-lower), Class Mid-point (upper+lower ÷2).
Types of Class Intervals:
- Exclusive Method: Upper limit of one = lower limit of next (0-10, 10-20).
- Inclusive Method: Classes don't share boundaries (0-9, 10-19).
- Open-end Classes: First/last class has no clear limit (Below 10, 10-20, Above 20).
PRESENTATION OF DATA
Textual: Data described in paragraphs.
Tabular (Tabulation): Data in rows & columns. Parts: Table Number, Title, Captions (column headings), Stubs (row headings), Body, Unit of Measurement, Source, Footnotes.
Diagrammatic/Graphic: Visual data representation.
ONE DIMENSIONAL DIAGRAMS
Use only length/height.
Line Diagram: Lines show values.
Simple Bar Diagram: Single bars for each category.
Multiple Bar Diagram: Multiple bars for comparison.
Sub-divided Bar Diagram: Bars divided into parts.
Percentage Bar Diagram: Bars show percentages.
TWO DIMENSIONAL DIAGRAMS
Use length & width (area).
Rectangles, Squares, Pie Diagrams (most common).
Pie Diagram Construction: Values → Percentages → Multiply % by 3.6 to get degrees. (100% = 360°). Example: Food 40% = 144°, Rent 30% = 108°.
THREE DIMENSIONAL DIAGRAMS
Use length, width, height (volume). Cubes, Cylinders, Spheres.
GRAPHIC PRESENTATION
Histogram: Bar chart for continuous data (bars touch).
Frequency Polygon: Line graph joining mid-points of histogram bars.
Frequency Curve: Smooth curve through polygon points.
Ogive (Cumulative Frequency Curve): Shows cumulative frequencies. Two types: Less than Ogive (adds from below), More than Ogive (adds from above).
IMPORTANT EXAM QUESTIONS
1. Prepare frequency distribution for given marks using exclusive method (6-8 marks).
2. Explain the basis of classification with examples.
3. Distinguish between different types of class intervals.
4. Explain the parts of a table with structure.
5. Construct a pie diagram from given percentage data.
6. Differentiate between Histogram, Frequency Polygon, and Ogive.