Class marks in exams
Use this diagram to explain the characteristics of z-scores.
Select crosses to show the calculation of the student's z-score and display an interpretation in terms of standard deviations from the mean.
Use the pop-up menu to display marks for the English exam. Explain that the mapping of marks to z-scores changes — the English marks are lower so a z-score of zero corresponds to a lower mark (the average in the class).
Any student's z-score indicates his/her position within the class — the best students get over +1 and the weakest students get under -1, irrespective of the difficulty of the exam.
The data are artificial. They describe the warping (measured as a bending angle) of 3 metre lengths of wood which have been left for 1 week at various temperatures.