Sampling in Research & Job Advertisements

Sample and Population

• Sample refers to a specific group selected for data collection.
• Size of the sample is always less than the total population size.
• Population consists of all individuals or items of interest.

Examples of Sample and Population

• IT job advertisements in the Netherlands:
  • Sample: Top 50 search results as of May 1, 2020.
• Eurovision Song Contest:
  • Sample: Winning songs performed in English.
• BSU Bokod Campus:
  • Sample: 200 undergraduate volunteers from three colleges.

Types of Data

• Data can be classified into various categories:
  • Raw, grouped, ungrouped, primary, secondary.
• Raw Data: Original form of information.
• Grouped Data: Organized into tables with class intervals and frequencies.
• Primary Data: Collected directly by the researcher.
• Secondary Data: Originally collected by others and published.

Variables and Measurement

• Variables represent characteristics or attributes that can take various values.
• Measurement involves assigning a value or label to a sample unit.
• Experimental Unit: The subject or object measured for a variable.

Classification of Variables

• Qualitative Variables: Non-numerical categories (e.g., Civil Status).
• Quantitative Variables: Numerical measurements.

Statistics Fields

• Two main fields of statistics:
  • Descriptive Statistics:
    • Focus on data collection, classification, and presentation.
    • Examples include measures of central tendency (mean, median), variability, etc.
  • Inferential Statistics:
    • Draws conclusions about populations using samples.
    • Involves methods like hypothesis testing and estimation.

Levels of Measurement

• Four levels of measurement:
  • Nominal: Only categorizes data (e.g., ethnicity).
  • Ordinal: Categorizes and ranks data (e.g., language ability).
  • Interval: Categorizes, ranks, and has equal spacing (e.g., temperature).
  • Ratio: All properties of interval plus a true zero point (e.g., weight).

Examples of Classification

• Ethnicity: Nominal
• Car Brands: Nominal
• Olympic Medalists: Ordinal
• Language Ability: Ordinal
• Likert-Type Questions: Ordinal
• Province of Birth: Nominal
• Test Scores: Interval
• Personality Inventories: Interval
• Temperature (Fahrenheit/Celsius): Interval

Applications of Measurement Levels

• Additional examples for classification:
  • Color: Nominal
  • Height: Ratio
  • Class Rankings: Ordinal
  • Age: Ratio
  • Survey Responses: Ordinal
  • Weight: Ratio
  • Calendar Dates: Interval
  • Temperature (Kelvin): Ratio
  • Types of Animals: Nominal