EC220/EC221
Introduction to Econometrics/Principles of Econometrics
计量经济学考试代写 Initially, the course is offered to and taken by all students whose birthdays fall on the 1st to the 15th of a month.
Specimen Exams Questions
Instructions to candidates
This paper contains two questions. Answer two questions. All questions will be given equal weight (50%).
Time Allowed Reading Time: 15 minutes
Writing Time: 1 hour
You are supplied with: No additional material
You may also use: No additional material
Calculators: Calculators are allowed in this exam
“If at any point in this assignment/exam you feel that anything is unclear, please make additional assumptions that you feel are necessary and state them clearly.”
Write concise answers. Precise arguments will be rewarded; however, accuracy is more important than including extensive details. Including irrelevant information in your answers will not improve your marks and will reduce the time you have to answer the questions directly. Marks will be deducted for incorrect irrelevant information.
1.The London School of Econometrics (LSM) plans to introduce an additional remedial math course to its first-year students. 计量经济学考试代写
Initially, the course is offered to and taken by all students whose birthdays fall on the 1st to the 15th of a month. At the end of the first academic year, LSM wants to examine whether the new math course improves the overall first year results. To this end, an analyst runs the following regression:
Aggregate First Year Marki= 𝛼 + 𝛽Extra Coursei+ 𝛾Aggregate A level scorei+ 𝑒i (1)
where Extra Course𝑖 is a dummy (binary) variable taking a value of 1 if the student took the extra course, and 0 if they did not. The analyst also collects information on each student’s high-school PE(physical education) performance (PE Performance𝑖) and the number of hours spent on extracurricular activities (𝐸𝑥𝑡𝑟𝑎𝑐𝑢𝑟𝑟𝑖𝑐𝑢𝑙𝑎𝑟𝑖 ) during the first year.
a)(5 marks) What is the interpretation of 𝛼?
b)(10 marks) What do you expect the value of the coefficient 𝜋1 to be in the following regression and why?
Aggregate A level scorei= 𝜋0 + 𝜋1Extra Course𝑖 + 𝑒2i(2) 计量经济学考试代写
c)(15 marks) Do you agree with the regression specification (1) to investigate the causal effect of attending the remedial math course on the first-year aggregate performance or would you specify the regression differently? Particularly, would you drop the variable Aggregate A level score𝑖 or add any other variables to Equation (1)? Explain why?
d)(10 marks) How would the result from the regression (2) in (b) affect your decision whether to interpret 𝛽 as the causal effect of the math course?
e)(10 marks) The head of the LSM counselling service asks whether the remedial course particularly helps students entering with weaker academic credentials. How would you specify a regression to answer this question? Be precise and explain the interpretation of any relevant coefficient.
2.The Ministry of Truth is interested in a rumour that regular social media use can affect academic performance. An analyst, Winston Smith, is tasked to do research on the effect of social media use. 计量经济学考试代写
He conducts a survey of 19,840 university students aged 19 to 26, randomly chosen from 200 universities in the city Airstrip Two. The key variable for “social media use”, 𝑆𝑜𝑐𝑖𝑎𝑙 𝑀𝑒𝑑𝑖𝑎𝑖 , is a dummy variable equal to 1 if the individual 𝑖 has been using social media regularly over the past academic year. Running regressions with standardised academic performance, 𝐴𝑐𝑎𝑑𝑒𝑚𝑖𝑐 𝑃𝑒𝑟𝑓𝑜𝑟𝑚𝑎𝑛𝑐𝑒𝑖 , on the left side, he obtains the following results: 
Notes. Robust standard errors are in the parentheses. 𝑂𝑣𝑒𝑟𝑠𝑒𝑎𝑠𝑖 = 1, if 𝑖 is an overseas student, and 0 otherwise.
a)(10 marks) Give a story why regular social media use may have a positive causal effect on academic performance, and a different story why it may have a negative causal effect.
b)(15 marks) To push forward a new campaign on social media, a politician interprets the coefficient in Column (1) and claims that “the data were collected using a random sampling process so we can establish causality from Column (1). There is a positive causal effect of regular social media use on academic performance among university students”. Explain why the politician is wrong. 计量经济学考试代写
c)(10 marks) Julia, another analyst, reacts to these results and claims: “Column (2) says that students from overseas who regularly use social media have lower academic performance than those who don’t.” Is she right or wrong? Explain why.
d)(10 marks) How would you conduct a statistical test that social media use has no effect on academic performance of home students at the 5% significance level using column (3)? If you can,derive the result of this test from the information in the table. If you can’t, explain why. Note that the critical values for t-statistics are 𝑡0.05,∞ = 1.645, 𝑡0.025,∞ = 1.96, 𝑡0.01,∞ = 2.326, 𝑡0.005,∞ = 2.576.
e)(5 marks) Do overseas students have more or fewer friends than home students do? Explain how you arrive at your answer.
