Answer
a.
mean = $132.55$
median = $(10th+11th)/2 = (134+136)/2=135$
mode = $144$
b. 10% trimmed mean = $132.688$
Work Step by Step
a.
mean =
$(107+109+111+113+116+121+126+127+132+134+136+138+139+141+144+144+150+151+153+159)/20 = 132.55$
10% trimmed mean, we remove 2 values from both ends and get
$111,113,116,121,126,127,132,134,136,138,139,141,144,144,150,151$
trimmed mean = $(111+113+116+121+126+127+132+134+136+138+139+141+144+144+150+151)/16=132.688$
