2008 First Semester STATS课程官方问答贴

z-score

原帖由 303B25 于 2008-3-14 10:30 发表
Question: For questions asking whether certain events form a partition, what's the best way to explain it? I usually answer by stating whether all the probabilities add up to one and whether they ...

Hi, yeah what you said is perfectly fine. Now, have you had a look at my past assignment resources? In there you can find the full written explanation to your question.

z-score

原帖由 303B25 于 2008-3-14 11:09 发表


I just looked at that, neat hand writing. Thanks a lot, I'll have a look tonight when I have more time. :'( Accounting assignment due in 50 mins.

Thank you, good luck with the accounting assignment.

z-score

原帖由 qian.qian 于 2008-3-14 20:48 发表
1. Jenny is planning to go tramping next weekend. The weather forecast indicates that there is a 40%
chance of rain, a 50% chance of wind and a 30% chance that there will be rain and wind. The s ...

恩，你说得很对，很聪明。

To 303B25, yep both of you guys got it right.

落水

LZ是个大好人啊～～～～～～～～～～～～

水鱼皇后

One of the main tourism sites in Wellington is the cable car. The lower station is just off the main
street and it is a quick ride up to the Kelburn station at the top of the hill. At the top are some
stunning views all over Wellington (if the notorious local weather is permitting). There is also a small
lunch bar, a restaurant, a new cable car museum and access to the Botanic Gardens. The Cable Car is
very popular with tourists as it is centrally located, offers great views and is relatively quick. When
cruise ships stop in Wellington for the usual one-day stay, there are often queues, even outside the
usual commuter rush hours.
The City Council’s tourism office is very interested in what tourists think of this major tourism
experience. As a result they employed a student to do a very quick interview with a minimum of 200
people at the area at the top of the Cable Car. The student had to do the work in the week before
Christmas. In addition, the tourism office installed a touch-screen survey computer at the back of the
cable car museum. The survey on the computer took about 5 minutes and asked questions in English.

What are the likely problems with sampling in the first approach?
感觉到不对 可是具体是什么又说不出 in the week before xmas 这里有问题吧？可以给点hint吗？

chanel

很好很好~~~~~~太有帮助了

luvwei

原帖由 mayigo 于 2008-3-11 01:55 发表
Study 1: A marketing manager for a chain of 64 small bakeries was interested in how different special offers affected sales. 20 of the bakeries were randomly chosen to have a special offer where  ...

所以楼主

是不是这三个都没有placebo???

z-score

原帖由 luvwei 于 2008-3-16 13:16 发表



所以楼主

是不是这三个都没有placebo???

是的，你说得很对。

luvwei

???????????????

z-score

原帖由 luvwei 于 2008-3-16 14:02 发表
???????????????

这三个study都没有placebo.

luvwei

我做了一个box plot

他的形状就是一个很正常的形状

我要怎么comment on it

luvwei

z-score

原帖由 luvwei 于 2008-3-16 14:03 发表
我做了一个box plot

他的形状就是一个很正常的形状

我要怎么comment on it

你要comment他的median, distribution(left skewed or right skewed, or symmetric), 最后他有一个trick, 就是实际上boxplot看不出来data有一个很大的gap, 你从stem and leaf plot能看出来。

z-score

原帖由 luvwei 于 2008-3-16 14:09 发表

Sorry, 我比较慢，你看一下我的worked examples, 里面答案会有帮助。

luvwei

第五题的那个表格阿

最后打出来的东西最后要包括什么呢？？

因为他说redraw...and bla bla

我print出来的table只有 page number, word lengh , word density

and mean word length at the end..

is that right???


or i need to print out the whole table wif everything in it????


thank you thank you

z-score

原帖由 luvwei 于 2008-3-16 14:40 发表
第五题的那个表格阿

最后打出来的东西最后要包括什么呢？？

因为他说redraw...and bla bla

我print出来的table只有 page number, word lengh , word density

and mean word length at the end..

...

你到4楼里面找一下去年的Assignment 1答案。那里的表格就是你第五题所需要的表格。

ztswyz

999999一道书上的例题 atom 帮忙啊


我怎么连书上的例题都不会了呢

这是一个stat题
貌似可以用r程序做

Q1

H0：u＝35
n= 25
mean= 37.77
sd=3.66
se=0.732


用r可以算出
p-value=0.0008996

哪个大虾告诉我这个r是怎么算得...

Q2


顺便问一下 如果已知95％ confidence interval 得出 83.75 ,84.24
如何反算...
或算 83 的p-value

z-score

不好意思，阿童木周末有点忙，今天上午我会解答从72楼到89楼的所有问题。

请稍等，谢谢支持。


更新：

所有问题已经回答完毕。

[ 本帖最后由 z-score 于 2008-3-17 10:48 编辑 ]

z-score

原帖由 水鱼皇后 于 2008-3-16 07:39 发表
One of the main tourism sites in Wellington is the cable car. The lower station is just off the main
street and it is a quick ride up to the Kelburn station at the top of the hill. At the top ar ...

原帖由 303B25 于 2008-3-16 10:13 发表
1) The people traveling during the week before Christmas might behavedifferently to people not traveling during that time. (Consider mostpeople travel between Christmas and New Years, retail wo ...

Thank you 303B25.

Addional to 303B25's response, this survey has a lot of non-response bias, like the people who can't understand English might refuse to do the interview completely.

If the day has very bad weather, not a lot of people will come up to the top of the mountain to start with.

This survey may have interviewer effect as the survey could be done using a computer or through an interviewer.

Hope this helps.

z-score

原帖由 ztswyz 于 2008-3-17 08:38 发表
999999一道书上的例题 atom 帮忙啊


我怎么连书上的例题都不会了呢

这是一个stat题
貌似可以用r程序做

Q1

H0：u＝35
n= 25
mean= 37.77
sd=3.66
se=0.732


用r可以算出
p-value=0.000 ...

Q1 R code

test.statistic <- (37.77-35)/(3.66/sqrt(25))
2*(1-pt(abs(test.statistic),25-1))

Hope this works!

Q2

没太看懂，反算什么东西？那个confidence interval的P-value?

z-score

原帖由 qian.qian 于 2008-3-16 16:10 发表

下面这两句话应该怎么写啊...
"None of the cars with dodgy steering wheels are missing both windows and passenger
seats. The cars without steering wheels fortunately have both wi ...

None of the cars with dodgy steering wheels are missing both windows and passenger seats.

IP(W AND P|D) = 0

z-score

原帖由 qian.qian 于 2008-3-16 16:32 发表
3. Basement Rentals is a dubious car rental outfit based in Auckland. Prices are cheap, but so is the
quality of the rental cars! Each car either has a reasonable steering wheel, a dodgy steerin ...

嗯，意思就是这个，但是解释怎样写出来你可以参考我的past assignment answers, 那种写法老师会接受.

希望能有帮助．