已知四个水果商店苹果的单价和销售额,要求计算这四个商店苹果的平均单价,应该采用()
A. 简单算术平均数
B. 加权算术平均数
C. 加权调和平均数
D. 几何平均数
某系200名学生统计学考试成绩分组资料如下表所示:200名学生的平均成绩为()
A. 80
B. 76.5
C. 82.1
D. 73.6
算术平均数、调和平均数、几何平均数均受极端值影响。 ( )
A. 对
B. 错
Lesson 6 背景知识听力填空[音频]When the departing aircraft has approached the________of active runway, the ground controller will _____ it to the _________. On receiving the pilot’s request for takeoff, the tower controller will look down the runway to determine whether the runway is __________to use. The tower controller will give the pilot _______ only when _______ has been achieved between aircraft. Once the aircraft _________, the tower controller will continue to watch the airplane and monitor its________ until this aircraft is ________ to the controller in the next control unit. When the aircraft approaches the ________, the approach controller hands it over to the tower controller. If conditions permit, the tower controller__________ to the pilot. When the aircraft has landed, the tower controller directs the pilot to ___________ and change to the _________.