Table 2 Questions and the expected challenge level assigned by the researchers

A researcher needs to sterilize the following items: (a) a solution of vitamins, (b) contaminated hospital linen, and (c) Petri dishes. Which method(s) will you suggest for each? Give reasons for the method(s) you have chosen.

Easy - Students come across these materials very often in their laboratory sessions and, therefore, also with the methods to sterilize each one of them. It is an extremely basic knowledge that is expected of a microbiology/biotechnology student.

A food preparer did not wash his hands and probably introduced 50 Escherichia coli cells in the dish. E.coli doubles every 20 min, and the dish has been kept outside for about 4 h. If 200 cells degrade 1 g of the dish, determine how many grams of the dish will be degraded at the end of 4 h.

Moderate - In this question, the students needed to recognize the exponential growth pattern of the introduced bacteria to correctly calculate the total number of cells at the end of the given time period. The question required the application of simple arithmetic logic given the doubling time of the bacteria. The second part of the question that asks for the amount of degraded dish was introduced to avoid asking the final cell count directly. The calculation for the degradation of the dish was not considered for the final scoring: Information that should have been provided for students to calculate the degraded amount was missing in the question (and would have made for a very challenging mathematical exercise).

Give your comments on the following: A doctor has just finished removing a patient’s infected kidney and is hurriedly moving to treat another patient who has suffered from burns. So, he quickly wipes all his instruments with a cotton swab dipped in phenol and proceeds to wash them with soap water, then treats the patient who has burns.

Difficult - This was an open-ended question; very different from the format that students are exposed to in their regular assessments. Also, no specific instruction was provided to students as to what was expected in their comment.