Edexcel Statisics 1

Edexcel Statisics 1

1. Correlation, Regression

   • PMCC
     • Coding
   • Interpretation
     • eXplanatory, response
     • meaning of correlation in context
     • gradient: for every extra 1 in x, you get an extra m in y
     • intercept: when x is zero, y is expected to be c
   • Extrapolation

2. Summary Statistics

   • Standard Deviation
     • Variance
   • Mean
     • Estimate from Grouped Data
   • Median and Quantiles
     • n+1 for individual items, just n for grouped data
     • Skew
       • Formal definition
         • for positive: o (Q2-Q1) < (Q3-Q2), i.e. right side of box fatter o OR mean > median > mode, i.e. the lump of the mode happens early on, then there's more spread on the positive side o 3(mean - median) / sd
     • Outliers: 1.5xIQR away from quartiles
     • Interpolation
       • it's basically about how far through the relevant class our wanted figure is.: (how many items into this group) / (frequency of this group) x class width + class lower bound
   • When Comparing Data, USE YOUR ASS!
     • Comment on: o averages (whichever is handy) o spread (sd, iqr, range) o skew use proper statistical names for things, not just "average" or "spread"

3. Graphs and Charts

   • Stem and leaf
   • Histogram
   • Cumulative Frequency
     • Curve for continuous, "steps" for discrete
   • Box plots

4. Probability

   • Discrete Random Variables
     • Expectation and Variation
       • Expectation Algebra, Var(aX+b), E(aX+b)
     • Cumulative Probability F(x)
     • simultaneous equations, use sum of p = 1
   • Normal distribution
     • if you have a prob. or a %, do reverse-lookup in tables to get z value
   • Trees
   • Venn Diagrams
     • Work from the intersections outwards, P(A) means the whole circle
     • Remember the BOX
   • GIVEN THAT means DENOMINATOR
   • Independent events: P(A) x P(B) = P(AnB)