statistics

UNIT 1: DATA HANDLING

Key Notes:

  • Primary vs Secondary data
  • Bias, reliability, validity
  • Sampling methods: random, stratified, systematic

Quiz Prompts:

  1. Explain why stratified sampling is often more representative than random sampling.
  2. Identify one source of bias in a questionnaire.

UNIT 2: REPRESENTING DATA

Key Notes:

  • Pie chart angle = (frequency / total) × 360
  • Histogram: frequency density = frequency / class width
  • Cumulative frequency used for median + quartiles

Quiz Prompts:

  1. Calculate frequency density for a class of width 5 with frequency 20.
  2. Why must histograms use frequency density instead of frequency?

UNIT 3: MEASURES OF LOCATION & SPREAD

Key Notes:

  • Mean = Σx / n
  • Weighted mean = Σ(xf) / Σf
  • IQR = Q3 − Q1
  • Standard deviation measures spread

Quiz Prompts:

  1. Why is median better than mean for skewed data?
  2. Compare two data sets using IQR and median.

UNIT 4: BIVARIATE DATA

Key Notes:

  • Cor