未知题型 设某零件的重量X~N(μ,σ2),其中μ=15,σ2=0.05,技术革新后,抽查6个产品,测其重量(单位:克)为:14.7 15.1 14.8 15.0 15.2 14.6.已知方差不变,问所生产零件的平均重量是否仍为15(克)?(取显著性水平为0.05)
单项选择题 根据短文回答 31~35 题。 The Barbie Dolls In the mid 1940's,the young ambitious duo(一对艺人)Ruth and Elliot Handler, owned a company that made wooden picture frames.It was in 1945 that Ruth and Elliot Handler joined with their close friend Harold Mattson to form. a company that would be known for the most famous and successful doll ever created.This company would be named Mattel,MATT for Mattson.and EL for Elliot.In the mid 1950's,while visiting Switzerland,Ruth Handler purchased a German Lilfi doll.Lilli was a shapely, pretty fashion doll first made in 1955.She was originally fashioned after a famous cartoon character in The West German Newsletter,Build.Lilli is the doll that would inspire Ruth Handler to design the Barbie doll.With the help of.her technicians and engineers at Mabel,Barbie was born。Ruth then hired Charlotte Johnson,a fashion designer,to create Barbie's wardrobe.It was in 1958 that the patent for Barbie was obtained.This would be a fashion doll unlike any of her time.She would be long limbed,shapely, beautiful,and only 11.5 inches tall.Ruth and Elliot would name their new fashion doll after their own daughter,Barbie.In 1959,the Barbie doll would make her way to the New York Toy Show and receive a cool reception from the toy buyers.Barbie has undergone a lot of changes over the years and has managed to keep up with current trends in hairstyles,makeup and clothing.She is a reflection of the history of fashion since her introduction to the toy market.Barbie has a universal appeal and collectors both young and old enjoy time spent and memories made with their dolls. 第 31 题 When Ruth and Elliot Handler were young.they had a strong desire( )A.to go to school.B.to take photos.C.to make wooden frames.D.to be highly successful.
未知题型 设自动包装机包装的每袋盐的净重服从正态分布,按规定每袋的标准重量为1 kg,标准差不能超过0.02 kg.某天开工后,从装好的食盐中随机地抽取9袋,测其净重为(单位:kg): 0.994 1.014 1.02 0.95 1.03 0.968 0.976 1.048 0.982 问这天包装机工作是否正常?(α=0.05)