Consultation paper
Presenting data in graphs, charts and tables —
science subjects
This edition: November 2015 (version 1.0)
© Scottish Qualifications Authority 2015
Contents
Presenting data in graphs, charts and tables — science subjects ....................... 1
Rationale ......................................................................................................... 1
Mark allocation ................................................................................................ 1
General marking principles for graphs, charts and tables in both internal and
external assessment ........................................................................................ 3
Biology and Human Biology ............................................................................. 5
Chemistry ...................................................................................................... 10
Physics .......................................................................................................... 12
November 2015 version 1.0
Consultation paper
Presenting data in graphs, charts and tables —
science subjects
This guidance document relates to internal and external assessment of National Qualifications in
Biology, Chemistry, Environmental Science, Human Biology, Physics and Science. It provides
teachers, lecturers and assessors with advice and guidance on the use of different formats for the
presentation of data.
A graph is a visual representation of data. Some graphs can be used to determine the relationship
or trend between variables. Values not measured can be estimated from some graphs using
extrapolation (extending the best fit line beyond either the first or last point plotted) or interpolation
(estimating a value between two plotted points).
Rationale
As far as possible skills taught in science should be transferable across science subjects to ensure
that learners studying more than one science are not disadvantaged. To ensure consistency the
general marking principles provided in this document should be applied to graphs, charts and
tables across the sciences.
Question Paper
Within question papers SQA has responsibility for ensuring that the type of data used allow
learners to readily recognise the type of presentation format and that the skills required for
interpreting data are appropriate to the format used.
Assignments/Projects (National 4–Advanced Higher)
As part of Course assessment for National Qualifications learners are required to select data
and present it in an appropriate format. The formats used should be in line with the principles
in this document. If particular data is commonly presented in a format other than a format
suggested in this document, then the commonly used format should also be acceptable.
Mark allocation
Question Paper
Not all graph questions will have the same mark allocation. The number of marks allocated
will depend upon:
 what the learner has to complete in terms of scales, labels, plotting, joining of points,
best fit line and identifying rogue points
 the complexity of the data
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Assignments/Projects (National 4–Advanced Higher)
Specific Marking Instructions will provide detailed mark allocations.
Different types of data are represented using different types of graph or chart. It is important
that:
 the correct type of graph is drawn
 a line appropriate for the data is drawn
 only skills appropriate to the graph type are assessed
Format
Line graph
Type of data
line of best
fit
(a straight
line or
curve)
Two continuous variables where a
change in the dependent variable
is caused by a change in the
independent variable.
Two continuous variables where a
change in the dependent variable
is not caused by the independent
variable.
or
Where confounding variables may
be masking any mathematical
relationship.
or
One continuous variable and one
discrete variable.
One continuous variable and one categoric
variable.





One continuous variable or classes with a
numerical range and the frequency, percentage
or number.
 presenting information
 selecting information
 examine the distribution
of the data
point-topoint
(adjacent
points
joined by a
ruler)
or
Stick/spike
graph
Bar chart
or Pie
chart
Histogram
Skills that can be
assessed
 presenting information
 selecting information
 determining a
mathematical relationship
 identifying a trend
 extrapolation
 interpolation
 calculating a gradient
 calculate the area under
the line without using
calculus
 explain changes in shape
SQA Consultation paper: Presenting data
presenting information
selecting information
identifying a trend
explain changes in shape
calculation of the area
under a graph line (eg
displacement/time or
velocity/time) without
using calculus
 presenting information
 selecting information
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General marking principles for graphs, charts and tables in both
internal and external assessment
Graphs
Axis and plotting
 Each axis should be labelled with the variable name and unit.
 Abbreviations for axis labels are acceptable where it is clear what the abbreviation
means.
 If SI units are abbreviated then only the standard abbreviation is acceptable. For non
SI units, symbols or abbreviations in normal use (eg min for minute) will also be
acceptable.
 If a scientific multiplier is used, it may be included with the axis label or units.
 Spelling errors should not be penalised unless it is not clear what the learner means
or if the spelling is too close to another word, eg ‘angle of defraction’ is not
acceptable as it is not clear if this means diffraction or refraction.
 Each axis should be marked with an appropriate scale. The scale should be of a size
that allows the points to be easily read or use at least half of the graph paper or grid.
 A common zero at the origin is acceptable if appropriate for the data.
 If a zero is not included on the scale this will not be penalised if the location of the
zero is implied by the rest of the scale.
 Major and minor grid lines should be included to allow the accuracy of processing to
be checked.
 A scale break or a scale not starting at zero is acceptable if appropriate for the data.
 Points/bars/spikes should be plotted such that the marker can check the accuracy,
with a tolerance of half the smallest division.
 If all points/bars/spikes are on major or minor grid lines then the detailed Marking
Instructions may indicate that no tolerance will be applied.
Line graphs
 Normally the independent variable should be plotted on the X (horizontal) axis and
the dependent variable on the Y (vertical) axis.
 Plotted points should be clearly distinguishable from the graph grid lines and the line
drawn.
 If points should be joined or a line drawn then this must be appropriate for the data
being presented.
 For data requiring a line of best fit the following will be accepted at the level
indicated:
— National 4 — accept a reasonable attempt at a line of best fit or point-to-point,
ie adjacent data points joined with a ruler
— National 5 — accept a reasonable attempt at a line of best fit (not point-topoint)
— Higher — accept a good attempt at a line of best fit
— Advanced Higher — accept a good attempt at a line of best fit
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 When multiple lines are plotted then it should be clear, either from labelling or the use
of a key, what each line represents.
 Interpolation and extrapolation are only appropriate for a line of best fit.
Bar charts
 Bar charts may be drawn either vertically or horizontally depending upon the number
of categories and length or complexity of the category labels.
 Normally the X axis represents the different categories and so has no scale. As the
categories are discrete, a gap should normally be left between the bars.
 A common zero at the origin is not normally acceptable.
Pie charts
 All lines should originate from the central point.
 A 2° tolerance is acceptable unless ‘tick marks’ are given and the divisions are
exactly on the ‘tick marks’.
Histograms
 The X axis should have a continuous scale or be divided into classes with a
numerical range.
 As the X axis is continuous there should normally be no gaps between the columns
representing the different classes.
 The Y axis should be the frequency, numbers or percentage in each category.
Tables
 Column headings should contain the variable name and units.
 Abbreviations for headings are acceptable where it is clear what the abbreviation
means. Spelling errors will not be penalised unless it is not clear what the learner
means.
 If SI units are abbreviated then only the standard abbreviation is acceptable. For non
SI units, symbols or abbreviations in normal use (eg min for minute) will also be
acceptable.
 Where a unit is not given in the heading but is given in the column it must be given
for every value.
 Values should be quoted to the same number of significant figures as the measured
data. However a tolerance of one fewer or up to two more is acceptable.
 Figures can be converted to scientific notation.
 The scientific multiplier may be included with the units in the table heading.
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Biology and Human Biology
Line graphs
Continuous variables are normally measured on a linear numerical scale. When the range of
values for one variable is large a logarithmic scale can be used.
Most commonly in Biology we would expect candidates to be dealing with quantitative data
where:
It is not certain (or known) that the change in the dependent variable is caused by the
independent variable
or
Confounding variables or random variation may be masking any mathematical relationship.
The presentation format for this type of data is a line graph with straight lines joining the
points.
Example: point to point
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When there are sufficient data points to be confident in the relationship or because, from
theory, there is good reason to believe that the intermediate values fall on the line, the
appropriate presentation format is a line of best fit.
Example: line of best fit
Bar graphs
Bar graphs are used to display and compare the number, frequency or other measure for
different discrete categories of data. The length of each bar is proportional to the value it
represents. The bars can be drawn either vertically or horizontally depending upon the
number of categories and length or complexity of the category labels.
Bar graphs can also be used for more complex comparisons of data with grouped bar
graphs and stacked bar graphs. Grouped bar graphs are a way of showing information about
different sub-groups of the main categories where a separate bar represents each of the
sub-groups. In stacked bar graphs the bars representing the sub-groups are placed on top of
each other to make a single column.
Example: vertical (column) bar graph
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Example: horizontal bar graph
Example: grouped bar graph
Example: stacked bar graph
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Pie charts
A pie chart shows data where the categories are proportions of a whole. The ‘pie’ is divided
into segments that represent this proportion. This is done by dividing the angles at the
centre. The entire pie represents the total data set and each segment of the pie is a
particular category within the whole.
Example
Behaviour of pigs in an enclosure
Histograms
A histogram is a graphical representation of the distribution of numerical data. It is an
estimate of the probability distribution of a quantitative variable. Due to the large number of
possible values the data are grouped to reduce the number of data points.
Example
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Tables
Candidates will often present raw, final or processed data in a table.
Examples
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Chemistry
Line graphs
Line graphs are used to process/analyse data consisting of two continuous numerical
variables where a change in the independent variable causes a change in the dependent
variable.
When the range of values for a variable is large, a logarithmic scale can be used.
Due to uncertainty in measurements, all data points will not normally lie on a single straight
line or curve. By examining the scatter of points candidates are expected to form a
judgement as to whether a best fit straight line or curve is appropriate. No line should be
drawn if the data points do not support either a straight line or curve.
Line graphs can be used to determine the relationship between the variables, and, by
calculating the gradient of a straight line, to determine the value of a constant.
40
35
Volume of Hydrogen / cm3
30
25
20
15
10
5
0
0
2
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4
6
Time / mins
8
10
12
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Bar charts
Bar charts are used to present data consisting of one variable that is continuous and one
that is discontinuous.
The trend in a bar chart can be illustrated by drawing a trend line, which is a line of best fit
where the data points are at the centre of the top of each bar.
4000
Enthalpy of combustion / kJ mol-1
3500
3000
2500
2000
1500
1000
500
0
1
2
3
4
5
Number of carbon atoms
6
More complex data can be presented using a grouped bar chart.
Percentage by volume / %
80
Paraffins
60
Naphthenes
40
Aromatics
20
0
Saudi
Light
North Sea
Brent
South
Louisiana
Beryl
Crude oil source
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Physics
Line graphs
Line graphs are used to process/analyse data consisting of two continuous numerical
variables where a change in the independent variable causes a change in the dependent
variable.
When the range of values for a variable is large, a logarithmic scale can be used. An
example of this would be a Hertzsprung-Russell diagram in Higher or Advanced Higher
question papers.
Due to uncertainty in measurements, all data points will not normally lie on a single straight
line or curve. By examining the scatter of points candidates are expected to form a
judgement as to whether a best fit straight line or curve is appropriate. No line should be
drawn if the data points do not support either a straight line or curve.
Potential difference/kV
Line graphs are commonly used to determine the relationship between the variables, and, by
calculating the gradient of a straight line, to determine the value of a constant.
4·0
3·5
3·0
2·5
2·0
1·5
1·0
0·5
0
0
20
40
60
80
100
120
140
160
Distance / mm
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0·00
0·20
0·40
0·60
0·80
1·00
time / s
1·20
1·40
0·0
-5·0
-10·0
-15·0
-20·0
back emf / V
Sketching graphs
Candidates may be asked to sketch a graph or sketch an additional line on to a graph using
data given in the question. To do this accurately candidates may be required to mark certain
values on the axes and indicate a scale by having two values on the axis, one of which is
usually the origin. The specific requirements of sketch graphs are made clear in the
question, and acceptable responses are detailed in the relevant Marking Instructions.
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Bar charts
Bar charts are used to present data consisting of one variable that is continuous and one
that is discontinuous.
The trend in a bar chart can be illustrated by drawing a trend line, which is a line of best fit
where the data points are at the centre of the top of each bar.
Acceleration of trolley / m s-2
0·8
0·7
0·6
0·5
0·4
0·3
0·2
0·1
0
1
2
3
4
5
6
Number of elastics used to accelerate trolley
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