11.若間距h=168~178cm，f_i=16,h=4，則頻數(shù)密度為(      )

A.5/2                                                           B.2     

C.4                                                              D.6

12.某公司職工月薪3500元的人最多，月平均收入為3700元，則職工年薪的分布(      )

A.正偏                                                        B.負偏

C.對稱                                                        D.不能作出結(jié)論

13.發(fā)達國家人口按年齡分組繪制成的死亡率曲線是(      )

A.鐘形曲線                                                 B.U型曲線

C.J型曲線                                                   D.邏輯斯蒂曲線

14.某同學期末考試成績分別是75、88、94、91。這位同學期末成績的算術(shù)平均數(shù)是(      )

A.87                                                            B.85   

C.86                                                            D.88

15.對于數(shù)據(jù)61,68，75，75，81，83。其眾數(shù)是(      )

A.83                                                            B.75   

C.75和83                                                   D.沒有眾數(shù)