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EnglandStatistics

Summarising data

4 dot points across 4 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do you calculate and choose the right average for a data set?

Mode, median and mean for discrete and grouped data; estimating the mean of grouped data with midpoints; linear interpolation for the median; weighted and geometric mean; effect of changes and transformations on averages.
A focused answer to Edexcel GCSE Statistics on averages, covering mode, median and mean for discrete and grouped data, estimating the mean with class midpoints, linear interpolation for the median, weighted and geometric mean at Higher tier, and the effect of changes and transformations.
10 min answer →

How do you measure and compare the spread of a data set?

Range, quartiles, interquartile range, percentiles, interpercentile and interdecile range; choosing an appropriate measure of spread; pairing a measure of spread with a measure of central tendency.
A focused answer to Edexcel GCSE Statistics on measures of spread, covering range, quartiles, interquartile range, percentiles, interpercentile and interdecile range, choosing an appropriate measure, and pairing a measure of spread with the right average.
9 min answer →

How do you describe the shape of a distribution and decide whether a value is an outlier?

Skewness by inspection and by calculation; interpreting positive and negative skew; identifying outliers by inspection and using the quartile and standard deviation rules; commenting on outliers in context.
A focused answer to Edexcel GCSE Statistics on skewness and outliers, covering determining skewness by inspection and the skewness formula, interpreting positive and negative skew, identifying outliers using the quartile and standard deviation rules, and commenting on outliers in context.
9 min answer →

How do you measure spread with standard deviation and compare values from different data sets?

Standard deviation for a set of values and for grouped data; using the mean and standard deviation to compare data sets; standardising values with the standardised score to compare across distributions.
A focused answer to Edexcel GCSE Statistics (Higher tier) on standard deviation and standardised scores, covering the standard deviation formulae for a set of values and grouped data, comparing data sets with the mean and standard deviation, and standardising values to compare across distributions.
10 min answer →