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Area

Owned by Joseph Baxter
Mar 20, 2015
2 min read

Description

Tests a candidates ability to define an area on an image.

Rationale

The Image Hotspot question is good for questions which require the students to click anywhere within a certain area but are no good in assessing the area itself. Clicking in the centre of the Right Atrium of the heart is much easier than defining the area of the Right Atrium.

Fit Criterion

Presentation

  • Image types supported include: GIF, PNG and JPEG.
  • Toolbar to include an optional magnifying glass mode which follows the mouse where is goes.
  • Only a single area can be included in this question type.
  • Editing capabilities to include:
    • Click and hold with the mouse for free-form drawing
    • Click and release for point to point drawing
    • Double-click to insert and point and close the shape (i.e. connect with start point)
    • Once a shape is complete: 1) black squares allow points to be moved, and 2) white circles allow a line to be split into two.

Marking

Two marking methods are available:

  • Mark per Option - student scores zero or full marks.
  • Allow partial Marks - student can score zero, full marks or partial marks.

Marking, whether full or partial, is based around percentage overlaps between the student answer and the correct answer. To stop a student just drawing around the whole image and scoring 100% overlap, the Area question has an error percentage which is the student area outside of the correct area. Staff can edit the correct and error percentages as required for both full and partial marks.

Feedback

Feedback includes:

  • Percentage of student answer within the correct area.
  • Percentage of the student answer outside the correct area (can exceed 100%).
  • Toolbar to allow toggling of:
    • Student answer on/off.
    • Correct answer on/off.
    • Area of error (different between student and correct answers) on/off.
  • General textual feedback for the whole question.
  • If standard setting has been used this should be displayed
  • List of learning objectives that the question is linked to
  • Student mark out of possible number.

Limited Save

After a question has locked it should only be possible to change the following aspects:

  • The correct area
  • Available marks and percentage tolerances
  • General feedback
  • Status - only 'Normal' or 'Retired' (not 'Incomplete', 'Experimental' or 'Beta')
  • Bloom's Taxonomy
  • Keywords
  • Teams

Standard Setting

  • There is only one rating per question.

Data Format

Correct Answer

Note: Only one correct answer is currently supported.

The area is stored in the 'correct' field in the options table. These are pairs of x/y coordinates for each point in the area stored in hexadecimal format.

Student Answer

  1. Split user_answer field by the semicolon.
  2. Split first part by a comma
    1. Percentage difference (inside and outside) between student answer and correct area
    2. Percentage of student answer within shape
    3. Percentage of student outside the shape
    4. Raw pixel count of student answer that overlaps (inside) the correct area (var li1)
    5. Raw pixel count of student answer that is outside of the correct area (var li2)
    6. Raw pixel count of correct area not covered by student answer (var li3)
  3. Split second part by a comma
    1. These are pairs of x/y coordinates for each point in the area stored in hexadecimal format.