12) The mean top of knee height of a sitting male is 20



12) The mean top of knee height of a sitting male is 20.7in.

H0: [pic]=20.7, H1: [pic]

15) Plain M&M candies have a mean weight that is a least 0.8535g.

H0: [pic]0.02, H1: [pic]

19) Right-tailed test;a=0.01

Critical value=2.33

20) Left-tailed test;a=0.05

Critical value=-1.645

12) Travel Through the Internal.Among 734 randomly selected internel users,it was found that 360 of them use the internet for making travel plans(based on data from a Gallup poll).Use a 0.01 significance level to test the claim that among internet users,less than 50% use it for making travel plans.Are the results important for travel agents?

H0: [pic] H1: [pic]

z-statistics=(360/734-0.5)/sqrt((360/734)*(374/734)/734)=-0.52

critical value=-z(0.01)=-2.33

since z- statistics>-2.33, we can not reject H0.

Conclusion: among internet users, at least 50% use it for making travel plans.

It is very important to travel agent, with many people using internet to make travel plan, the travel agent should improve their website to attract more customer.

13) Percentage of E-mail users.Technolongy is dramatically changing the way we communicate.In 1997,a survey of 880 U.S. households showed that 149 of them use e-mail(based on data from The World Almanac and Book of Facts).Use those sample results to test the claim that 15% of U.S. households use e-mail. Use a 0.05 significance level.Is the conclusion vaild today?Why or why not

H0: [pic] H1: [pic]

z-statistics=(149/880-0.15)/sqrt((149/880)*( 731/880)/880)=1.53

critical value=z(0.025)=1.96

since z- statistics ................
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