Representations have purposes
Use a table to organise and retrieve exact values, a column graph to compare distinct categories, a line graph to show change across continuous time, and a labelled visual or physical model to show selected structures, scales or relationships. More than one representation may be useful when purposes differ.
Build an informative table
Give every column a precise heading and unit. Keep conditions and their results aligned, preserve repeated trials separately, and calculate summaries such as a mean only when useful. Never alter an unusual value merely to create a neat pattern.
Choose graph variables
Place the changed or ordered variable, such as time, on the horizontal axis and the measured outcome on the vertical axis. Category labels belong on a column graph; continuous time data commonly suit a line graph.
Construct graphs accurately
Add a descriptive title, label both axes and units, choose sensible equal numerical intervals, plot every value against the source table and provide a key for multiple series. An unmarked truncated or uneven scale can exaggerate or distort differences.
Describe patterns and trends
Read from left to right and identify increase, decrease, stability, peaks, plateaus, repeated cycles or changes in rate. Support descriptions with values or comparisons and include exceptions rather than forcing all points into a perfect trend.
Describe relationships carefully
Paired data can show that two variables tend to increase together, decrease together or show no clear relationship. This is an association. A graph alone does not prove that one variable caused the other; another factor may influence both.
Use models scientifically
A model represents selected features of a real object, system or process. State its purpose and scale where relevant. Evaluate both what it makes easier to see and what it omits, simplifies or distorts.
Scale and model limits
A larger model is not automatically more accurate. Accuracy depends on whether relevant proportions, positions, relationships and labels match the stated purpose. A solar-system model may scale distance while simplifying planet size, or vice versa.
Compare representations
A table may be best for exact lookup while a graph makes a trend visible and a labelled diagram shows structure. Select or combine forms deliberately, then explain how each feature helps communicate the evidence.
Interpret within the evidence
Interpolation estimates between measured points; extrapolation extends beyond the observed range and is more uncertain. Report what the representation supports, qualify claims to the sample and distinguish direct measurements from estimates and explanations.