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AUTHOR Marco Steenbergen PUBLISHED May 5, 2024 Table of contents Instructions Problems Set 1 Set 2 References Instructions This homework covers IVs and RDDs. It is due on May 20 at 23.59 hours. The homework is to be completed in groups of 3 students. You should submit: The answers in the quiz tool on OLAT. This will provide instant feedback on your performance. An R syntax file via email to [email protected]. Without this file, you will not receive any points for the homework. Good luck! Problems Set 1 A university discovers that many students have to work while studying. It fears that the combination of work and study negatively affects scholastic performance. For this reason, the university administration decides to make available stipends to students. The policy is limited to students with parental incomes at 30 percent of the median or less. Since this still leaves too many students for the available budget, the administration also makes eligibility contingent on a standardized test and sets a minimum score of 80 out of 100 points. Those indigent students who score at least 80 receive a stipend, whereas others do not.1 The minimum test score is advertised ahead of the start of the stipend program. The university administration has asked you to evaluate the effect of stipends on performance, as measured by student’s GPA at the end of the year.2 It has collected the following data, which can be found in stipend.Rda: test is the standardized test score that was used to determine who is eligible to receive a stipend. motivation is a survey measure of student’s motivation that was taken in the summer before the academic year started and before the standardized test was taken. Higher scores mean that students are more motivated to succeed in their studies. gpa is the grade point average at the end of the academic year and serves as the outcome measure. Now answer the following questions. Using the approach of Imbens and Kalyanaraman (2012), what is the bandwidth you should use? Using a polynomial regression of order 3 and controlling for motivation, what is the estimate of the treatment effect? Based on appropriate tests, which of the following conclusions can you draw? Which of the following statements best describes when we perform a placebo test on the location of the minimum test score? The students at this university are an altruistic lot. Someone discovers that a subset of students share their stipends with peers who did not meet the test score but still need the money. What assumption would this violate? Set 2 A team of scholars performs the following experiment on the effects of voting advice applications (VAAs) on voting behavior, specifically voting correctly (Lau and Redlawsk 1997). A random sample of 1000 respondents is drawn. Half of the sample is randomly assigned to the treatment, which means they receive a letter encouraging them to use a VAA. The other half do not receive such encouragement. Voting correctly is coded 1 if someone’s vote corresponds to what it would have been under full information. Among those who were encouraged to use a VAA, the proportion of people who voted correctly was 0.35. Among those who were not, that proportion was 0.30. Since encouragement does not equate actual treatment intake, the team of scholars also recorded whether someone had actually used a VAA. The team obtains the following information: Of those encouraged to take the treatment, 250 did use a VAA. Of those assigned to the control group, 300 individuals did not use a VAA. Based on the information and what you know from the lecture, please answer the following questions. What is the intention-to-treat effect? How many always-takers are “hiding” among those who used a VAA and were encouraged to do so? What is the compliance rate? What is the LATE? The authors find that those encouraged to use a VAA also tended to watch more news about the election. What, if any, assumption is being violated here? References Imbens, Guido, and Karthik Kalyanaraman. 2012. “Optimal Bandwidth Choice for the Regression Discontinuity Estimator.” The Review of Economic Studies 79 (3): 933–59. https://doi.org/10.1093/restud/rdr043. Lau, Richard R., and David P. Redlawsk. 1997. “Voting Correctly.” American Political Science Review 91 (3): 585–98. https://doi.org/10.2307/2952076. Footnotes You may assume that everyone who is eligible to take the stipend also does and that no one who is not eligible can receive the money.↩︎ GPA = grade point average. For this exercise, we assume the university is located in the United States and uses a grading scale from 0 to 4. On this scale, 0 means F (fail), 1 corresponds to a grade of D, 2 to a grade C, 3 to a grade of B, and 4 to a grade of A.↩︎

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Answer to a math question AUTHOR Marco Steenbergen PUBLISHED May 5, 2024 Table of contents Instructions Problems Set 1 Set 2 References Instructions This homework covers IVs and RDDs. It is due on May 20 at 23.59 hours. The homework is to be completed in groups of 3 students. You should submit: The answers in the quiz tool on OLAT. This will provide instant feedback on your performance. An R syntax file via email to [email protected]. Without this file, you will not receive any points for the homework. Good luck! Problems Set 1 A university discovers that many students have to work while studying. It fears that the combination of work and study negatively affects scholastic performance. For this reason, the university administration decides to make available stipends to students. The policy is limited to students with parental incomes at 30 percent of the median or less. Since this still leaves too many students for the available budget, the administration also makes eligibility contingent on a standardized test and sets a minimum score of 80 out of 100 points. Those indigent students who score at least 80 receive a stipend, whereas others do not.1 The minimum test score is advertised ahead of the start of the stipend program. The university administration has asked you to evaluate the effect of stipends on performance, as measured by student’s GPA at the end of the year.2 It has collected the following data, which can be found in stipend.Rda: test is the standardized test score that was used to determine who is eligible to receive a stipend. motivation is a survey measure of student’s motivation that was taken in the summer before the academic year started and before the standardized test was taken. Higher scores mean that students are more motivated to succeed in their studies. gpa is the grade point average at the end of the academic year and serves as the outcome measure. Now answer the following questions. Using the approach of Imbens and Kalyanaraman (2012), what is the bandwidth you should use? Using a polynomial regression of order 3 and controlling for motivation, what is the estimate of the treatment effect? Based on appropriate tests, which of the following conclusions can you draw? Which of the following statements best describes when we perform a placebo test on the location of the minimum test score? The students at this university are an altruistic lot. Someone discovers that a subset of students share their stipends with peers who did not meet the test score but still need the money. What assumption would this violate? Set 2 A team of scholars performs the following experiment on the effects of voting advice applications (VAAs) on voting behavior, specifically voting correctly (Lau and Redlawsk 1997). A random sample of 1000 respondents is drawn. Half of the sample is randomly assigned to the treatment, which means they receive a letter encouraging them to use a VAA. The other half do not receive such encouragement. Voting correctly is coded 1 if someone’s vote corresponds to what it would have been under full information. Among those who were encouraged to use a VAA, the proportion of people who voted correctly was 0.35. Among those who were not, that proportion was 0.30. Since encouragement does not equate actual treatment intake, the team of scholars also recorded whether someone had actually used a VAA. The team obtains the following information: Of those encouraged to take the treatment, 250 did use a VAA. Of those assigned to the control group, 300 individuals did not use a VAA. Based on the information and what you know from the lecture, please answer the following questions. What is the intention-to-treat effect? How many always-takers are “hiding” among those who used a VAA and were encouraged to do so? What is the compliance rate? What is the LATE? The authors find that those encouraged to use a VAA also tended to watch more news about the election. What, if any, assumption is being violated here? References Imbens, Guido, and Karthik Kalyanaraman. 2012. “Optimal Bandwidth Choice for the Regression Discontinuity Estimator.” The Review of Economic Studies 79 (3): 933–59. https://doi.org/10.1093/restud/rdr043. Lau, Richard R., and David P. Redlawsk. 1997. “Voting Correctly.” American Political Science Review 91 (3): 585–98. https://doi.org/10.2307/2952076. Footnotes You may assume that everyone who is eligible to take the stipend also does and that no one who is not eligible can receive the money.↩︎ GPA = grade point average. For this exercise, we assume the university is located in the United States and uses a grading scale from 0 to 4. On this scale, 0 means F (fail), 1 corresponds to a grade of D, 2 to a grade C, 3 to a grade of B, and 4 to a grade of A.↩︎

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It looks like you've provided details from a homework assignment involving Instrumental Variables (IVs) and Regression Discontinuity Designs (RDDs) along with a randomized controlled trial scenario. Let’s address each of the key questions posed in the problems you listed: ### Set 1: RDD on University Stipends 1. **Bandwidth using Imbens and Kalyanaraman (2012) Approach** - To determine the optimal bandwidth for the RDD analysis, you would typically use software packages that implement the bandwidth selection method suggested by Imbens and Kalyanaraman. These methods generally involve estimating the density of the running variable (test scores) around the cutoff and minimizing the mean squared error of the estimator. 2. **Estimate of Treatment Effect Using Polynomial Regression** - For this analysis, you would fit a polynomial regression of order 3 on the data, with test scores as the running variable, controlling for motivation. The coefficient on the treatment variable (stipend eligibility) within this regression would provide the estimated treatment effect on GPA. 3. **Placebo Test Explanation** - A placebo test in this context would typically involve analyzing the treatment effect at a cutoff point other than the actual cutoff used (test score of 80) to see if any significant effects are observed. If significant effects are found at other cutoffs, it could indicate that your original findings might be due to factors other than the stipend policy. 4. **Assumption Violated by Stipend Sharing** - If students share their stipends, this could violate the assumption of the exclusion restriction in IV analysis. The exclusion restriction assumes that the instrument (eligibility for the stipend) affects the outcome (GPA) only through the intended channel (receipt of the stipend), not through other pathways like enhanced peer support or shared financial resources. ### Set 2: Randomized Trial on Voting Advice Applications (VAAs) 1. **Intention-to-Treat Effect** - The intention-to-treat (ITT) effect is the difference in the proportion of people voting correctly between those encouraged to use a VAA and those not encouraged. Calculation: \(0.35 - 0.30 = 0.05\). 2. **Always-Takers in the Encouraged Group** - Always-takers would be those who would use the VAA regardless of whether they were encouraged or not. Since the control group had no encouragement, those in the control who used a VAA could be considered always-takers. However, without knowing how many in the control used the VAA despite not being encouraged, a precise number of always-takers in the encouraged group cannot be determined. 3. **Compliance Rate** - The compliance rate among those encouraged can be calculated as the proportion of the encouraged group that followed through and used the VAA. Calculation: \( \frac{250}{500} = 0.50 \) or 50%. 4. **Local Average Treatment Effect (LATE)** - LATE would be calculated for those who complied (used the VAA when encouraged). This requires an estimation method like 2SLS to properly adjust for the compliance behavior. 5. **Violation of Assumptions by Additional Media Exposure** - The increased likelihood of watching election news among those encouraged to use the VAA may violate the assumption of independence between the instrument (encouragement) and other variables influencing the outcome (voting correctly). This introduces confounding, complicating the interpretation of the VAA’s effect as isolated from other influences.

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