Note: Use the Question Bank Editor on-screen dialog boxes for setting the margin of error in numeric and numeric-with-unit questions.
For an introduction to the concept of margin of error, see Controlling Answer Tolerance.
The exact answer is not always required. In EDU, you can specify a margin of error, within which student responses are graded correct, for any mathematical question type. You can specify a margin of error for answers that are static or defined using algorithmic variables.
Use "?" in the answer field to set a margin of error. The ? (plus or minus) operator represents "+/-" in ordinary math notation. You can specify an absolute tolerance. For example, to accept 2.5 +/- 0.25, that is, any response between 2.25 and 2.75 (inclusive), use 2.5 ? 0.25. You can also specify a percentage tolerance. To accept 5.12 +/- 5%, that is, any response between 4.864 and 5.376 (inclusive), use 5.12(1 ? 0.05).
Note: The ? operator cannot be used in an algorithmic variable definition (or other algorithmic statement).
For numeric and Maple-graded questions, you cannot use the "?" operator. For information on specifying a margin of error for a numeric question, see Setting Answer Tolerance in Numeric Questions. To specify a margin of error in a Maple-graded question, use Maple code.
Consider the following when working with margins of error:
Precedence of the ? Operator: The ? operator is of the same precedence as "+" and "-". For example, 2*3 ? 0.5 is the same as 6 ? 0.5 and 2*(3 ? 0.5) is the same as 6 ? 1.
Units: Because expressions with units have different dimensions from pure numbers, you must specify a dimensioned margin of error for a dimensioned answer. To specify "2kg with a tolerance of 0.1kg", enter 2kg ? 0.1kg or (2 ? 0.1)kg. To specify "50cm within 5%", enter (1 ? 0.05)50cm.
Important: The expression 50cm ? 2 is invalid. It is a mixed expression. The left-hand side has dimension length. The right-hand side is dimensionless (a pure number).
The ? operator is not available to students: A student cannot specify a margin of error. The above issues do not arise for students.
For more examples and information, see Tutorial: Margin of Tolerance in Answers.
See Also: