Diagnostic paragraphs allow instructors to assess the writing ability of their students. The instructor can the provide feedback so the students can improve areas of weakness as well as point out the writers' strong points.
In a typical diagnostic paragraph exercise, the instructor will assign the students the task of reading a passage from a written work. The student must then write a paragraph about the work based on a prompt provided by the instructor.
The instructor will evaluate the students' writing based on a number of factors. These may include the strength of the opening sentence, how well the writer maintains focus on one idea, how well the main idea is developed and accuracy in spelling and grammar.
In addition to serving as a way for an instructor to evaluate writing skills, he can also use the diagnostic paragraph as an introductory activity. Students can share their paragraphs with the rest of the class as a way to facilitate getting to know one another.