Worked example
A cooling display marks minutes on the x-axis and temperature in degrees Celsius on the y-axis. Trial J reads 54°C at minute 3 and 43°C at minute 8. Trial K reads 49°C and 41°C at the same times. J is still warmer at minute 8 but has cooled by 11°C, compared with 8°C for K.
Contrast and common error
For bars, a baseline of 40°C makes values of 42°C and 44°C look very different in height: the bars extend 2 and 4 degrees above the baseline. From zero, they extend 42 and 44 degrees, so their relative heights are similar. A line graph instead marks positions; a tighter scale can help you see changes. Read the printed scale before subtracting. A difference between series at one time does not say which changed more.
Transfer check
A chart marks water depth in 5-cm ticks. The depth moves from the first tick above 20 cm to the second tick below 20 cm. Find the change. Check: the readings are 25 and 10 cm; the change is −15 cm, a decrease of 15 cm.
Try it, then explain it.
Complete a short set without looking at the example. After each answer, explain which evidence or rule supports your decision and why the alternatives do not fit.
Sources & authorship
Original OpenExam explanations and examples. References support the concepts; they are not the source of copied questions. Independent educator review is pending.
OpenStax Physics 2.3 Position vs Time GraphsONS Service Manual Axes and Gridlines