Worried Teacher meets Dexter!!!

Today we will not be talking about any new technology rather we will be having a conversation between a confused teacher who doesn’t know how to evaluate her students assessments and a know it all professor who is up-to date with online assessment tools.

 Lema: I am worried about my students tests results and I don't know if the problem is with my questions or my students as they aren’t performing well in my course. This is a question that keep running in my head over and over !! help me please !!

Dexter (annoyingly genius): Hmmm…. so you want to know if your questions are not too easy or too difficult for students to solve?

Lema: Yes ... I also want to know if my questions could help me distinguish between high achieving and low achieving students. In other words, I want to make sure that a student who had a high score in the test will succeed to answer the question and students who have low scores will simply fail to answer the question.

Dexter: So you need to find the difficulty and discrimination of your questions?

Lema: .Oh yes … I guess that is what I meant.

Dexter: Well, that is easy to do. Have your students attempted the tests in a virtual learning environment ???

Lema: Haaa !!! virtual learning environment  !!!

Dexter: Chill….I meant something like Moodle[1] or Blackboard[2]?

Lema: No no I didn’t, I still don’t know why you asked that

Dexter: Because Moodle and Blackboard simply provide you with this information. After students finish the test you could see which questions were easy and hard. Anyways you don’t need a virtual learning environment to answer your question

Lema:Ok what should I do?

Dexter : Insert your data into an Excel[3] or OpenOffice Calc[4] sheet, don't tell you have never used them?

Lema: I did .. I did

Dexter : Ok insert your data ( contain students test answers) into Excel or OpenOffice Calc and calculate the difficulty for each question by dividing the number of students who answered the question right by the total number of student who attempted the question. If the value is low the question is considered difficult and if the value is high the question is easy.

Lema: Great. what about discrimination ?

Dexter :Well, there are different ways to calculate discrimination. I will start with the simplest one. Arrange students in an ascending order according to their total scores..Then find the difference in percentages of correct answers to a question between the top quartile and the bottom quartile students.

Lema: Ok

Dexter : It is also worth saying that some researchers choose the top third and bottom third students. You could also use something called the point perseial coefficient it finds the association (correlation) between the question score and total test score[5]. I noticed Moodle used it to calculate the discrimination

Lema: Thank you

Dexter: No worries.. I hope you find it useful …. I am sorry to tell you that this didn’t answer your question !!!! Difficulty and discrimination depends totally on the sample of students answering your question so it is hard to know if the problem is with your questions or your students simply didn’t study well.

Lema : What !!!

Dexter: Don’t worry there is a solution for that and it is called Item Response Theory[6]. I will explain it to you later … Bye for now !

References

[1] Moodle https://moodle.org

[2] Blackboard http://uki.blackboard.com/sites/international/globalmaster/

[3]Microsoft Excel http://office.microsoft.com/en-gb/excel/

[4]OpenOffice Calc http://www.openoffice.org/sc/

[5]Point Perseial Coefficient http://docs.moodle.org/25/en/Item_analysis_theoretical_background

[6]Item Response Theory http://echo.edres.org:8080/irt/