2008 First Semester STATS课程官方问答贴

dk7

5. Find a function g(x) such that

P(g(X) <= x) = P[X <= ginv(x)] = x (x is the cdf of U[0,1])

I'll tell you the long way. We have

1 - exp (- lambda * ginv(x)) = x

So some manipulations will give you ginv.  Get the inverse of that will give you g(), the answer.

dk7

6th question

P[X <= x, Y <= y] = P[U <= x, 1 - U <= y] = P[U <= x]P[1 - U <= y] = um... I should stop here
: )

mayigo

Question 4. [ 9 Marks ] [First half of Chapter 10]
A member of the union representing fast-food restaurant workers is interested in whether the law
change had an effect on the length of time before new employees received their first pay rise. The
union representative randomly sampled 20 New Jersey fast-food restaurants and recorded values for
Incr1 and Incr2, the length of time (in months), for a new employee, until the first pay rise before
the law change and after the law change.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Incr1 4 4 4 4 26 13 13 12 10 13 13 6 26 26 26 26 26 26 26 15
Incr2 52 26 26 26 40 26 26 24 20 20 18 10 26 26 26 26 26 26 26 14
(a) Using SPSS, draw the appropriate box plot(s) for this data set. (You should consider the design of
this study to ensure the relevant plot(s) is drawn.) Comment on any features in the plot(s).
请问lz这里的boxplot用spss应该怎么做呢？要计算他们inr1和inr2的差吗？

spirithell

阿童木，恩师呀，


stat 101 A3
Question 6. [ 15 Marks ] [Chapters 9 and 10]
Use the information on the variables given on page 2 of this assignment to answer this question.
(a) For each of the scenarios 1 to 5 below, write down the name of the variable(s) (given in the table on
page 1) needed to examine the question and for each variable, write down its type (qualitative or
quantitative).

我是不是就把变量的名字和类型写下来就行了？
like scenario 1: full1 full2 ?
太那个什么了吧？您能不能把scenario 1 做出来，看一下是什么样子的？
A3 前5道题我都改了好几遍了，改来改去。。。。。
就为了8point!!!!呜呜~~~~

spirithell

Update Q6 (a)

Scenario 1:   donot hnow
Scenario 2:   do not know
Scenario 3: Burger King, StWage1 (quantitative)         Wendy’s, StWage1 (quantitative)
Scenario 4:         HrsOpen1 (quantitative)                HrsOpen2 (quantitative)
Scenario 5:         Price1 (quantitative)        Price2 (quantitative)        Region (qualitative)

(b)  tools doing now~~~~

(c)  CFDAF

Please help me check it, thanks lot, 8point~~~~~,   because my mid text is like faled...55555~~~

luvwei

atm 解释一下q6吧我也不懂了

luvwei

a) s1 full2 quantitative state qualatative？

c) EEDAF?

spirithell

Q7
(a)  比较了好几百字，累~~~

（b）什么意思？

下面的都讲讲吧！！！！　真的是很难～～～看懂什么意思．

[ 本帖最后由 spirithell 于 2008-5-21 14:05 编辑 ]

天外飞猪

ATM帮帮忙
我实在分不清楚什么情况下做的是1tail test还是2 tails test。lecture说大部分情况下作2 tail的。如果要做 1 tail的，题目会说得很清楚。可是course book上chapter 10 pg9题目没有说是要做1 tail的，table 的p value是2tails的。老师就说要除2。我都分不清楚为什么。请帮帮忙，不然assign都不会做了

z-score

sorry 今天在家生病，我现在来了。

z-score

原帖由 天外飞猪 于 2008-5-21 20:03 发表
ATM帮帮忙
我实在分不清楚什么情况下做的是1tail test还是2 tails test。lecture说大部分情况下作2 tail的。如果要做 1 tail的，题目会说得很清楚。可是course book上chapter 10 pg9题目没有说是要做1 tail的， ...

恩，one tailed test必须要有prior knowledge告诉我们mean or proportion是大于或小于hypothesised, otherwise always use a two-tailed.

z-score

原帖由 spirithell 于 2008-5-21 13:32 发表
Q7
(a)  比较了好几百字，累~~~

（b）什么意思？

下面的都讲讲吧！！！！　真的是很难～～～看懂什么意思．

Question 7
part a - comment on the plots

* mean or median, say which is the highest and list them in order.
* spread and range of the different samples
* distribution, like say symmetric or skewed
* Any outliers

---Comment is to compare the different samples, don't need to state actual values.

part b - copy the 4 assumptions for the F-test in the blue notes. Put the assumptions in context of the assignment question and that is it.

z-score

原帖由 luvwei 于 2008-5-21 01:15 发表
a) s1 full2 quantitative state qualatative？

c) EEDAF?

Isn't full 2 also qualitative? Cause it's 5 or fewer or 6 or more.

z-score

原帖由 mayigo 于 2008-5-20 17:52 发表
Question 4. [ 9 Marks ] [First half of Chapter 10]
A member of the union representing fast-food restaurant workers is interested in whether the law
change had an effect on the length of time be ...

恩，是的，这个boxplot是incr1和incr2的differences, 在SPSS里面，computer new variable, then define a new variable diff, then type incr1 - incr2, then draw a boxplot of it.

z-score

原帖由 luvwei 于 2008-5-21 00:41 发表
atm 解释一下q6吧我也不懂了

恩，每年的question 6都差不多，你看一下past assignment answers比较好。4楼

z-score

原帖由 dk7 于 2008-5-20 17:21 发表
6th question

P[X  

Thank you dk, I really appreciate your help.

ミ﹏龍.

阿童木啊，20x啲Assignment 04....第二题

当我想把factor里面的level换一个做baseline啲时候，R就会出现这个错误

> Setting<-factor(Setting,levels=c("A","B","C","D"))
> hardness.fit1<-lm(Hardness~Humidity+Setting)
错误于`contrasts<-`(`*tmp*`, value = "contr.treatment") :
  contrasts can be applied only to factors with 2 or more levels


为啥啊？~试了很多遍都不行

z-score

原帖由 spirithell 于 2008-5-20 19:58 发表
Update Q6 (a)

Scenario 1:   donot hnow
Scenario 2:   do not know
Scenario 3: Burger King, StWage1 (quantitative)         Wendy’s, StWage1 (quantitative)
Scenario 4:         HrsOpen1 (quantitative)                HrsO ...

先让你们讨论一下，周末我把正确答案分享一下。

z-score

原帖由 ミ﹏龍. 于 2008-5-22 23:42 发表
阿童木啊，20x啲Assignment 04....第二题

当我想把factor里面的level换一个做baseline啲时候，R就会出现这个错误

> Setting hardness.fit1

我做了一遍，好像可以运行，你要不从新在试一下？

> y <- lm(Hardness~Humidity+Setting)
> summary(y)
Call:
lm(formula = Hardness ~ Humidity + Setting)
Residuals:
     Min       1Q   Median       3Q      Max
-20.4132  -4.4584  -0.1249   5.2667  22.3376
Coefficients:
            Estimate Std. Error t value Pr(>|t|)   
(Intercept)  84.2129     9.6977   8.684 3.09e-07 ***
Humidity      1.9431     0.1386  14.021 5.01e-10 ***
SettingA    -86.5042     7.0942 -12.194 3.47e-09 ***
SettingC    -82.6143     7.2145 -11.451 8.17e-09 ***
SettingD     42.5156     7.0915   5.995 2.45e-05 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Residual standard error: 11.16 on 15 degrees of freedom
Multiple R-squared: 0.9787,     Adjusted R-squared: 0.973
F-statistic: 171.9 on 4 and 15 DF,  p-value: 2.463e-12

ミ﹏龍.

这个我可以做出来，但我要把Baseline换成A的时候，就会出现error~

z-score

原帖由 ミ﹏龍. 于 2008-5-23 13:59 发表
这个我可以做出来，但我要把Baseline换成A的时候，就会出现error~

我是从baseline = A换到B, code没有问题．很奇怪．

~Kurosagi~

question 1b 有人会做吗？？

~Kurosagi~

原帖由 spirithell 于 2008-5-20 19:58 发表
Update Q6 (a)

Scenario 1:   donot hnow
Scenario 2:   do not know
Scenario 3: Burger King, StWage1 (quantitative)         Wendy’s, StWage1 (quantitative)
Scenario 4:         HrsOpen1 (quantitative)                HrsO ...

我写了

S1 - Full 1 and Full2  quantitative
S2 - Part1 and Region 不知道
S3 - Chain and StWage1 不知道
S4 HrsOpen1 and HrsOpen2 - Quantitative
S5 Price2 and Region  不知道


不知道对不对

~Kurosagi~

你好好养病咯。。。。

t-multiplier

原帖由 ~Kurosagi~ 于 2008-5-23 17:35 发表
question 1b 有人会做吗？？

We don't know, because the true mean is unknown.

mumununu

Atom, help with 101 A3   Question 4 please......
when doing 4 b) i)   i suppose there is an outlier so do we have to do the t test twice ? once outlier inclusive and then outlier exclusive?

confusing...

spirithell

STAT101 A3 Q7  d  ,e

这两个问题怎么回答? 好像都在写文章似的.

另外问一下,STAT 201的写的东西多不多？如果多的话，我要改课程，太麻烦了~~~~~

spirithell

if u recong an outlier is exist, from (a), you should do .....  but i did not , its waste time.

you are right.

z-score

原帖由 mumununu 于 2008-5-23 20:31 发表
Atom, help with 101 A3   Question 4 please......
when doing 4 b) i)   i suppose there is an outlier so do we have to do the t test twice ? once outlier inclusive and then outlier exclusive?

c ...

Hi, could you show me the plot please? I don't think they'll give you guys an outlier in 10x.