The Winsorized mean can be calculated with the remaining values after replacing a certain number or the proportion of the values at the low and high end of the sorted data. First the data set is ordered from smallest to largest 3,3,4,5,6,6,7 then we will find how many data points will be replaced, k, since the winsorizing is 30% and there are 7 observations, the value of k is k = np = 7×0.30 = 2,1 which is nearly 2. Therefore, 2 observation from each end of the sorted data will be replaced with those next in magnitude, these observations are as follows, 3 is replaced with 4 and 7 and 6 is replaced with 6. The set yields to 4,4,4,5,6,6,6. The 30% Winsorized mean of the data set is (4+4+4+5+6+6+6)/7= 5. The answer is D.