Video 3.1 Sample variance and standard deviation
Discussion of the various different, but equivalent, formulae for the sample variance is presented with revision of the summation operator, 
. Application to simple data set performed and standard deviation derived. Duration: 10 minutes 17 seconds.
. Application to simple data set performed and standard deviation derived. Duration: 10 minutes 17 seconds.Click HERE
Video 3.2 Stem-and-leaf diagram
Key components of a standard stem-and-leaf diagram are presented with advice on how to maximise the number of marks when answering such a question in an examination. Consideration is also given to commenting on the shape of the distribution revealed by a stem-and-leaf diagram with reference to outliers and skewness. Duration: 20 minutes 29 seconds.
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Video 3.3 Histogram
Construction of a histogram is discussed with a review of the key points looked for by examiners. Due to bar areas being proportional to the frequency of observations, designing histograms to have equal category widths is recommended. Duration: 20 minutes 29 seconds.
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