Answer
a. mean = 958.35
median = 990
b. 20% trimmed mean= 986.083
Work Step by Step
a. mean = $27+441+530+595+699+716+872+930+933+934+1046+1065+1125+1127+1187+1199+1234+1274+1353+1480)/20 = 958.35 $
median = $(10th +11th)/2 = (934+1046)/2 = 990$
B. 20% trimmed mean, we remove 4 from both ends of the data, and we obtain $699,716,872,930,933,934,1046,1065,1125,1127,1187,1199 $
trimmed mean = $(699+716+872+930+933+934+1046+1065+1125+1127+1187+1199)/12 = 986.083$
