The table is the collection of the participants’ suggestion for every function.
(Not every suggestion given by every participant will be included here, but only common or similar suggestions, to avoid personal factor’s effect)
1. The participants are not picked randomly, which will make the result of UT biased.
Solution: No solution for this limitation, the only thing can be done is to analyze that whether the grades difference is resulted by this.
2. The participants will affect each other during the UT
Solution: The participant must be tested one by one