The approximate value calculated by the trapezoidal method is always greater than the actual value. This can be supported by the argument that value of ERROR= EXACT VALUE- APPROXIMATED VALUE comes out to be NEGATIVE which shows that approximated value is greater.

yes. I meant that the answer is specific to this question and not applicable for all functions. I don't know exactly which all functions it can be true but I guess it won't be true for any functions which is not monotonically increasing or decreasing.

In the wiki page it is given- overestimate for all concave curves and underestimate for all convex curves.