The trimmed or as it may sometimes be called as the truncated mean is a slightly modified version of the
arithmetic mean. Trimmed or truncated mean is calculated after a certain number or proportion of the lowest and highest observations from the sorted data are removed (trimmed) from the calculations. First, the data is ordered from smallest to largest, as follows, 2,3,4,5,6,6,7. Then we will find how many data points will be discarded, k, since the trimming is 30% and there are 7 observations, the value of k is k = np = 7×0.30 = 2,1 which is nearly 2. Therefore two 2,3,6 and 7 is removed from the set, which yields to 4,5,6. The sum, 15 is divided to n - 2k which is equal to 7 - 2*2=3 this results in the value 5.The answer is D.