GCSE Statistics

GCSE Statistics

1. Collecting Data

   • Sampling methods
     • Stratified
     • Systematic
       • Random starting place, every nth person where n is pop / sample
     • Random
       • Every item has an equal chance
       • Using random number tables
     • Quota
     • Key words: sampling frame, sampling unit, census, population
   • Capture / recapture is just two equiv fractions
     • tagged    tagged in recapture ---------  =  --------------------------- total               recapture size
   • Surveys
     • Suitable questions (open/closed)
     • Pilot surveys
   • Data types

2. Graphs and Charts

   • Histograms
   • CF / boxplots
     • Skew
     • Outliers
   • Choropleth
   • Comparative pie charts
     • Remember to comment on the proportions (angle of slice) and the actual numbers (area)
   • Stem and leaf digrams
   • Misleading graphs
     • Axes
     • Labels
     • Thickness / colour
     • 3D effect

3. Processing Data

   • Standard deviation
   • Mean
     • Use midpoints when data is grouped
   • Median/Quantiles by Interpolation

4. Correlation

   • Spearman's Rank
     • Tied ranks
     • Interpreting the result
   • Line of best fit
     • Equation of the line (gradient / intercept)
     • Make predictions
     • Extrapolation

5. Time

   • Index numbers
     • Get the scale factor or multiplier by doing: eventual value / original value
     • Chain-based
     • Base year
     • Weighted
   • Time series table and graph
     • Moving averages
     • Trend line
     • Seasonal variations
       • Mean seasonal variation / seasonal effect
         • Predict future value

6. Probability

   • Venn diagrams
     • Work from the inside out - remember P(A) is the probability of the whole A circle. Also, remember the box and the number of items outside the circles.
   • Tree diagrams

7. Distributions

   • Normal
     • Features, percentages
     • QA charts, warning, action limits
   • Binomial
   • Discrete uniform