Statistics topics

Statistics topics

1. Cumulative Frequency

   • CF charts
     • Calculate CF by summing frequencies
     • Plot at end of range
     • Read off median, UQ, LQ, etc.
     • They always go up, S -shape
   • Box plots
     • http://www.gcsemathstutor.com/cumulativefreq.php

2. Histograms

   • Frequency (area) = Frequency Density (y-axis) x Column width (x-axis)
     • http://www.bbc.co.uk/schools/gcsebitesize/maths/statistics/representingdata3hirev3.shtml
     • Find Median : half area either side
       • find other % splits

3. Describing / comparing data

   • 1 point per mark
   • Compare mean to mean, IQR to IQR, etc
   • Outliers

4. Bivariate data

   • Scatter graphs
     • Always draw a LOBF
       • Find and interpret gradient and y-intercept
     • Correlation
       • Positive, negative, weak, strong, none
       • Correlation does not imply causation
         • http://www.tylervigen.com/spurious-correlations
     • Interpolation (within data) OK, Extrapolation (outside range of data) BAD

5. Collecting data

   • Survey -> Sample Census -> Population
     • Pros / cons of sampling
   • Capture / Recapture
     • Equivalent fraction
   • Stratified Sampling

6. Grouped Data

   • Discrete / continuous data
     • http://intellspot.com/discrete-vs-continuous-data/
   • Easier to represent, but info is "lost"
   • Find the mean
     • Add the fx column
   • Frequency polygon
     • Plot at MIDPOINTS, join dot to dot, not to origin
   • Find the median
     • Total frequency is n, find the n/2 th item

7. Two way tables

   • Don't forget to include TOTAL row and column

8. Charts

   • Bar Charts
   • Pie Charts
     • Limitation - totals not obvious
   • Pictograms
   • Vertical Line Charts
     • http://wtmaths.com/vertical_line_charts.html
     • Discrete data
   • Time Series