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Statistical Investigation – Meaning & Steps

Statistical investigation is like detective work - collect clues (data), analyze them, and solve the mystery (draw conclusions)! 🔎

What is Statistical Investigation?

Definition: A systematic, scientific process of collecting, organizing, analyzing, and interpreting data to solve a specific problem or answer a research question.

Example Problems:

  • What is the average income of Indian households?
  • Is there a relationship between education and unemployment?
  • Which product features do customers prefer?

Steps in Statistical Investigation

Step 1: Formulation of the Problem

Define what you want to study.

Questions to ask:

  • What is the objective?
  • What exactly needs to be measured?
  • What is the scope (geographical, time period)?

Example:

  • Vague: "Study unemployment."
  • Clear: "Measure the unemployment rate among engineering graduates in Mumbai during 2023."

Step 2: Planning the Investigation

Decide HOW to collect data.

Key Decisions:

  1. Population vs Sample: Survey everyone or just a sample?
  2. Method: Census, Sample Survey, Experiment?
  3. Budget & Time: How much can we spend? Deadline?
  4. Resources: How many investigators needed?

Example:

  • To study TV viewing habits, decide: Online survey or door-to-door? How many people? Which cities?

Step 3: Collection of Data

Gather the actual information.

Two Types:

  1. Primary Data: Collected fresh for the first time (Survey, Observation, Experiment).
  2. Secondary Data: Already existing data (Government reports, past studies).

Methods:

  • Direct Personal Interview
  • Indirect Oral Interview
  • Questionnaires (Mailed/Online)
  • Observation

(We'll study these in detail in Chapter 10-11)

Step 4: Organization of Data

Arrange data in a meaningful way.

Sub-steps:

  1. Editing: Check for errors, incomplete responses.
  2. Classification: Group similar items (Age groups: 0-10, 10-20, etc.).
  3. Tabulation: Present in rows and columns.

Example: Raw data: 25, 30, 22, 35, 28... Organized Table:

Age GroupFrequency
20-303
30-402

Step 5: Presentation of Data

Display data visually for easy understanding.

Methods:

  • Tables: Rows and columns.
  • Charts: Bar, Pie, Line graphs.
  • Diagrams: Histograms, Ogives.

Golden Rule: A picture is worth a thousand words!

Step 6: Analysis of Data

Apply statistical techniques to extract information.

Techniques:

  • Measures of Central Tendency: Mean, Median, Mode.
  • Measures of Dispersion: Range, Standard Deviation.
  • Correlation: Relationship between variables.
  • Regression: Predictive analysis.

Example: From sales data, calculate: Average sales = Rs 5 lakh/month.

Step 7: Interpretation of Results

Draw conclusions and make decisions.

Questions to answer:

  • What do the numbers mean?
  • What actions should be taken?
  • Any recommendations?

Example: "Since average sales are Rs 5 lakh but target is Rs 7 lakh, we need to increase marketing efforts by 30%."

Flow Diagram

Problem Definition
      ↓
Planning
      ↓
Data Collection
      ↓
Data Organization (Editing, Classification, Tabulation)
      ↓
Presentation (Tables, Charts)
      ↓
Analysis (Averages, Dispersion)
      ↓
Interpretation (Conclusions)

Summary

  • Statistical investigation = Systematic research process.
  • 7 Steps: Problem → Plan → Collect → Organize → Present → Analyze → Interpret.
  • Each step is crucial - skip one, and results may be faulty.

The Bottom Line: Good investigation = Good data = Good decisions! 📊

Test Your Knowledge

Question 1 of 5

1. The first step in statistical investigation is:

Collection of data
Formulation of problem
Analysis
Presentation
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