Homework 1
1.开发办公室和注册商为您提供了以下内容的匿名匹配：

（a）108名学生的平均起薪为\$ 38,644.86，有标准差
\$ 7,541.40。为所有经济学的起薪点建立95％的置信区间

（b）心理学专业的类似样本表明起薪明显较低。

（c）您想知道通过计算经济学的平均薪水来获得好成绩是否值得

B +或更高\$ 39,915.25 \$ 8,330.21 59
B或更差\$ 37,083.33 \$ 6,174.86 49

2.考虑以下总体均值的替代估计量：
=（Y1 + Y2 + Y3 + Y4 + … + Yn–1 + Yn）

3.新闻杂志《经济学人》定期发布有关所谓的巨无霸指数的数据

Mac以当地货币定价为美元价格应等于之间的汇率

（a）将BigMac.xlsx数据导入RStudio。计算每个美国的预测汇率

（2.51美元）。也就是说，将一个变量添加到名为PredictedExRt的数据框中，该变量等于
BigMac价格除以2.51
（b）对实际汇率与预计汇率进行回归。如果购买

（c）将实际汇率与预计汇率作图。包括45度

（d）陈述PPP所依据的两个零假设。您应该使用单尾还是双尾替代假设？
（e）截距和斜率的t统计量是多少？
（f）使用5％的显着性水平，您对给定的原假设作出何决定？
t统计量？您使用了哪些关键值？您是否担心以下事实？

（g）使用学生的t分布必须做出哪些假设？
4. Use the data set called lead_mortality for this question (Read the description file first so you
know the variables). Import the file lead_mortality.xlsx into RStudio with name ‘leadmort’.
a. Write the R code that will provide the correlation matrix for all numerical variables. That
is the correlation between every numerical variable in the data set. Make sure not to
include the character variables (city and state) in this function.
b. Using your code in part (a) determine the variables that have highest and lowest
correlation with infant mortality rate.
c. Write the code to plot the scatter-plot of age against infant mortality. What does this
graph tell us? Does it make sense?
d. Do the same scatter plot in part (c) only for Ohio. Does the Graph for Ohio look similar
to the whole U.S? Explain. (Your answer should include both the code and the graphs as
well as your explanation)
e. Run the regression to see the effect of lead on infant mortality:
??????? = ?଴ + ?ଵ???? + ?
What is your estimate for intercept and sloe and their standard errors?
f. How do we test the hypothesis at 95% that lead causes infant mortality? What is your tstat? Given the t-stat do we have evidence that lead has effect on infant mortality?
g. Run the same regression for Ohio only and explain your results.
h. How many observations do we have for Ohio? What do you think about the validity of
the analysis in part (g) for Ohio?

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