Descriptive statistics
Frequency tables, graphs, measures of centre and spread, and worked IB exam questions for IB Applications and Interpretation SL.
Descriptive statistics summarises a set of data with a few tables, graphs and numbers so that you can compare them and draw conclusions. In the IB four skills are assessed above all: organising the data in frequency tables (with intervals if needed), reading them from graphs (histograms, cumulative frequency graphs, box-and-whisker diagrams), calculating the measures of central tendency (mean, median and mode) and the measures of spread (range, quartiles, variance and standard deviation). The GDC does the calculations; what is asked is that you know how to enter the data, interpret the result in context and decide which measure is the most appropriate.
Recommended order
Follow the sections in order: data and frequency tables, graphical representations, measures of central tendency, quartiles and box-and-whisker diagrams and variance and standard deviation. At the end you will find the IB exam questions grouped by type.
Working with fractions and decimals, and basic use of the graphic display calculator (GDC).
Sections in this topic
Data and frequency tables
Population and sample, variable types, absolute, relative and cumulative frequencies, and grouped data with class midpoints. IB Applications SL.
3 worked examples Section 2Graphical representations
Bar charts and pie charts, histograms with unequal class widths, frequency polygons and cumulative frequency graphs. IB Applications SL.
3 worked examples Section 3Measures of central tendency
Mean, median and mode with raw data, frequency tables and grouped data, using class midpoints and the modal class. IB Applications SL.
3 worked examples Section 4Quartiles and box-and-whisker diagrams
Range, quartiles, percentiles, interquartile range, outliers, box-and-whisker diagrams and quartiles from cumulative graphs. IB Applications SL.
3 worked examples Section 5Variance and standard deviation
Variance and standard deviation from tables and grouped data, how to read them, and how data changes affect them. IB Applications and Interpretation SL.
3 worked examples End of topicIB exam questions for topic 8
IB exam questions on descriptive statistics: frequency tables, graphs, measures of centre and spread, box plots, with step-by-step solutions.
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