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Published byKory O’Brien’ Modified over 5 years ago

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OCR Functional Skills Charts Presenting data – Good data presentation skills are important. – Poor graphs and tables lead to the wrong conclusions being drawn

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OCR Functional Skills Displaying your data – There are some good rules of thumb for displaying numerical data: Simple is always better Graphs, tables and charts can be used together Use clear titles and labels Provide descriptions of the main points Don’t compare variables with diiferent scales of magnitude

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OCR Functional Skills Choosing the best graph – Line graphs – These are used to display frequency distributions over time – The y-axis represents frequency – The X-axis represents time or different groups – Use different colours or patterned lines to represent different groups

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OCR Functional Skills – Line graphs can consist of straight lines or curved segments: Lines – use straight lines to connect ‘real’ data points Curves – use to represent functional relations between data points or to interpolate data – Use a line graph: To display long data rows To forecast data values To compare different graphs To find and compare changes over time To recognise correlation and variation between values

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OCR Functional Skills If the x-axis requires an interval scale To display interactions over two levels on the x-axis When it defines meaningful patterns (i.e. a zigzag line) – Do not use a line graph: If the x-axis has non-numeric values

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OCR Functional Skills – Bar charts – Use bar charts to: Present small data sets over a nominal (e.g. countries, testing conditions) or interval scale (e.g. time) Compare data – Do not use bar charts for: Comparisons – it is better to use one-dimensional scattergraphs because it is not dominated by bars or columns Larger data sets – use line charts instead

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OCR Functional Skills – Always try to arrange the groups that define the bars in a natural order – for example, age – If a natural order does not exist, define categories by name – Position the bars vertically or horizontally – Always make the bars the same width – The length of a bar should be proportional to the frequency of the event

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OCR Functional Skills – Clustered bar charts – Bars are presented as clusters of subgroups – These are useful for comparing values across categories – They are sometimes referred to as stacked bar charts

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OCR Functional Skills – Pie charts – This is a circular (360 o ) graphic representation of data – It compares groups or subgroups to the whole group or category using differently coloured or patterned segments – Segments may be pulled out of the pie for emphasis (an ‘exploded’ pie chart)

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OCR Functional Skills – Use pie charts to: Convey approximate proportional relationships (relative amounts) at a point in time Compare part of a whole at a given point in time Emphasise a small proportion of data – Do not use pie charts: For exact comparisons of values, because estimating angles is difficult To rank data – use column/bar charts in this case; use multiple column/bar charts for grouped data If proportions vary greatly – Do not use multiple pie charts to compare corresponding parts

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OCR Functional Skills Always exercise care in the use of pie charts – Pie charts cannot represent values beyond 100% – Each pie chart is valid for one point in time only – Pie charts are only suited to presenting percentage values – People find it harder to estimate angles than distances

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OCR Functional Skills How to create graphs Your teacher will now demonstrate how to create a chart using the coffee producers filecoffee producers file

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OCR Functional Skills Legends, titles and labels – Every chart should have a title that describes what it represents, such as ‘Sale of Chickens in November’ – If a bar chart or pie chart is being displayed then there is usually a legend – This is placed near the chart to describe what is represented in it – Some chart wizards will include a legend even if it is not required, in these cases delete it!

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OCR Functional Skills – Make sure axes are labelled and titled – Ensure the segments of pie charts are clearly labelled or a visible legend is provided – Sometimes both are needed

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OCR Functional Skills Printing charts – When you produce a chart it is almost certainly on the same screen as the data associated with it – If the chart is going to be used away from the spreadsheet, for instance for inserting into a newsletter, you may want to copy it separately from the data – Planning what data to use and what is not is an important skill to develop

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