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Activity focus

  • primary vs secondary data
  • missing value vs zero
  • unit consistency
  • real-world understanding of data

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Practice set

  1. Mark each as primary or secondary:
    • data from a field survey done by your team
    • published state health report
  2. Explain whether the following is valid:
    • heights stored as 155 cm, 1.62 m, 149 cm
  3. In a marks sheet, one student has no value entered. Another has 0.
    • are these the same?
    • explain why
  4. Suggest one better variable name than x for attendance.

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Answer key

    • field survey: primary
    • health report: secondary
  2. Not valid without standardization; units are mixed.
  3. No.
    • blank = missing data
    • 0 = recorded score/value is zero
  4. Example: attendance_percent

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Common mistakes

  • assuming any published number is automatically reliable
  • treating coding convenience as statistical correctness
  • ignoring missing values in analysis