OCR Practical Skills Handbook 

Tables

The following guidelines should be followed when presenting results in tables.

  • All raw data in a single table with ruled lines and border.
  • Independent variable (IV) in the first column; dependent variable (DV) in columns to the right (for quantitative observations) OR descriptive comments in columns to the right (for qualitative observations).
  • Processed data (e.g. means, rates, standard deviations) in columns to the far right.
  • No calculations in the table, only calculated values.
  • Each column headed with informative description (for qualitative data) or physical quantity and correct SI units (for quantitative data); units separated from physical quantity using either brackets or a solidus (slash).
  • No units in the body of the table, only in the column headings.
  • Raw data recorded to a number of decimal places and significant figures appropriate to the least accurate piece of equipment used to measure it.
  • All raw data recorded to the same number of decimal places and significant figures.
  • Processed data recorded to up to one decimal place more than the raw data.

 Graphs

The following general guidelines should be followed when presenting data in graphs.

  • The type of graph used (e.g. bar chart, histogram, line graph, pie chart or scattergram) should be appropriate to the data collected.
  • The graph should be of an appropriate size to make good use of the paper.
  • There should be an informative title.

Guidelines for specific types of graphs follow.

Bar charts and histograms

These are used when the dependent variable on the y-axis is discrete, i.e. whole numbers, fractions are impossible and the data under consideration deal with frequencies.

 Bar charts

Bar charts are used when the independent variable is non-numerical, e.g. the number of different insect species found on trees. These data are discontinuous.

  • They can be made up of lines, or blocks of equal width, which do not touch.
  • The lines or blocks can be arranged in any order, but it can aid comparison if they are arranged in descending order of size.
  • Each axis should be labelled clearly with an appropriate scale.

 Histograms

These are used when the independent variable is numerical and the data are continuous. They are sometimes referred to as frequency diagrams.

  • One axis, usually the x-axis, represents the independent variable and is continuous. It should be labelled clearly with an appropriate scale.
  • The number of classes needs to be established. This will largely depend on the type and nature of the data. However, five times the log of the number of observations is one approach.
  • The blocks should be drawn touching.
  • The edges of the blocks should be labelled, so a block might be labelled ‘7’ at the left and ‘8’ at the right; this is expressed as a class range 7 - 8 units but it is implied that 7.0 is included in this range but 8.0 is not. 8.0 will be included in the next class range, 8 - 9.
  • The other axis, conventionally the y-axis, represents the number or frequency, and should be labelled with an appropriate scale.

Pie charts

These can be used when displaying data that are proportions or percentages.

  • Sector angles are calculated by dividing their percentage by 100 and multiplying the answer by 360o (if figures are proportions then just multiply by 360o).
  • When comparing two or more pie charts, the sequence of segments should be the same.
  • The size of the pie circle can be made proportional to the size of the sample.
  • Pie charts should not contain more than 6 to 7 sectors, otherwise they become confusing.
  • There should be segment labels or a key.

 Line graphs

  • Straight lines should join points. A smooth curve is only drawn if there is reason to believe that intermediate values fall on the curve.
  • The independent variable should be plotted on the horizontal axis (x) and the dependent
  • variable plotted on the vertical axis (y).
  • Axis labels should be stated horizontally and in lower case, using SI units or in full.
  • Axes should have an arrow end when there is no scale. If the origin (0,0) is not included in a printed graph, the axis should be broken.
  • Points should be plotted with encircled dots (  ) or saltire crosses ( x ). When multiple curves are being plotted, vertical crosses (+) can be employed.
  • If a graph shows more than one curve, then each curve should be labelled to show what it represents.

Scattergrams

These are used when investigating the relationship between two variables of a sample or replicate and observations are in pairs. The data can then be used to establish if there is a relationship between the variables. The relationship can be a positive correlation, a negative correlation or no correlation at all.

  • The two axes of the graph are marked out with appropriate scales.
  • The two variables are plotted for each sample as a point so that each point on the graph represents an individual.

Annotations

Whilst a label might be the name of a tissue, an annotation adds a descriptive quality such as shape, size or colour.

Drawings from a microscope

  • Single, clear lines drawn with a sharp pencil.
  • No shading or colour on the diagram.
  • Informative title to be included.
  • Scale included (e.g. high power, low power, x80, x10) to show approximate magnification.
  • Low power tissue plans may not include cells.
  • High power diagrams show a few adjacent cells only; adjacent cells must have complete lines.
  • Cells or tissues should be in correct proportions.
  • Label lines drawn in pencil using a ruler

Command Words

Analyse Separate information into components and identify their characteristics.

Annotate To provide notes of explanation.

Apply Put into effect in a recognised way.

Assess Make an informed judgement.

Calculate Generate a numerical answer, with working shown.

Comment Present an informed opinion or infer points of interest relevant to the context of the question.

Compare Identify similarities.

Complete Write the information required.

Consider Review and respond to information provided.

Contrast Identify differences.

Deduce Draw conclusions from information provided.

Define Specify meaning of the word or term.

Demonstrate Provide clear evidence.

Describe Provide a detailed account (using diagrams/data from figures or tables where appropriate). The depth of the answer should be judged from the marks allocated for the question.

Determine The quantity cannot be measured directly but can be obtained by calculation. A value can be obtained by following a specific procedure or substituting values into a formula.

Discuss Give a detailed account that addresses a range of ideas and arguments.

Distinguish Recognise and identify difference(s).

Draw Produce a diagram or to infer.

Estimate Assign an approximate value.

Evaluate Judge from available evidence.

Examine Investigate closely.

Explain Set out reasons or purposes using biological background. The depth of treatment should be judged from the marks allocated for the question.

Identify Recognise or select relevant characteristics.

Illustrate Make clear by using examples or provide diagrams.

Interpret Translate information provided.

Justify Present a reasoned case.

Label To indicate (by using a straight line).

List Provide a number of points with no elaboration. If you are asked for two points then give only two!

Measure Establish a value using a suitable measuring instrument.

Name To provide appropriate word(s) or term(s).

Outline Restrict the outline to essential detail only.

Plot Mark out points on a graph or illustrate by use of a suitable graph.

Predict Suggest possible outcome(s).

Recall Repeat knowledge from prior learning.

Recognise To identify.

Record Report or note.

Relate Make interconnections.

Sketch Produce a simple, freehand drawing. A single clear sharp line should be used. In the context of a graph, the general shape of the curve would be sufficient.

State Produce a concise answer with no supporting argument.

Suggest Apply your biological knowledge and understanding to a situation which you may not have covered in the specification.

Summarise Present main points in outline only.

Use Apply the information provided or apply prior learning.

Additional Key Terms:

How: Describe in what way or by what means……

What: Provide specific information……

Why: Explain the reason or purpose……

Accuracy: The accuracy of an observation, reading or measurement is the degree to which it approaches a notional ‘true’ value or outcome. For example: closeness to a line of best fit; accuracy of apparatus on percentage error.

Precision: The ability to be exact (degree of precision).

Reliability: The measure of confidence that can be placed in a set of observations or measurements. For example: confidence limits of statistical tests or concordance of repeats or standard deviation.

Validity: The implication that the outcome of an activity is not being distorted by extraneous factors. 

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