Paper Reading 1: Overview

Concepts: Heterogeneity, Endogeneity, Exogeneity.
Methods: Balancing Test, Cross-cohort Design, Permutation Test with Resampling;

Gender Peer Effects on Students’ Academic and Noncognitive Outcomes: Evidence and Mechanisms

Jie Gong, Yi Lu and Hong Song, 2019, Journal of Human Resources

Data: China Education Panel Survey 2014 (CEPS 2014)

Challenge: Nonrandom grouping of students

• if there are unobserved characteristics of students that are associated with both gender composition in the classroom and students’ outcomes, the estimation of gender peer effects would be biased.
• To address this identification problem, researchers often exploit cross-cohort variation or use random assignment\

Solutions:
a) Cross-cohort Design : samples a cohort (a group of people who share a defining characteristic, typically those who experienced a common event in a selected period, such as birth or graduation) e.g., In order to research on the relationship between smoking & lung cancer, we match obs in terms of variables such as economic status and other health status so that the variable being assessed, the smoking(independent) can be isolated as the cause of the lung cancer(dependent).

Test for Randomization
b) Permutation test with a resampling approach

• for classroom i in grade j, school k:
  • for all student characteristics:
    • randomly draw 10,000 synthetic classrooms of the same size from the sample of all students from grade j, school k.
    • Calculate the average value for each characteristic within classroom i
    • Obtain an empirical p-value (proportion of the 10,000 resampled classrooms with lower statistics for the corresponding characteristic within the observed classrooms.)

c) Randomly drop observations and see whether regression results change dramatically.

Data Processing:

1. Noncognitive outcomes are obtained from students’ responses to eight survey items⇒use component analysis to classify the eight survey items into two categories: (1) the level of mental stress, and (2) the level of social acclimation and satisfaction in school.
2. Students’ academic performance is measured by test scores, supplement with test scores with students’ self-assessed performance scores.
3. Normalize each index to have a mean of zero and a standard deviation of one.
4. Conduct balancing test
   • Balancing test: female proportion (dependent)~ predetermined characteristics (independent). test the factor one-by-one. Null hypothesis: insignificant t-statistics, which means predetermined characteristics do not related to the proportion of female students.
5. Endogenous school choice. While random class assignment is conducted, students’ school choices may not be random⇒ introduce school-grade fixed effects $\lambda_{sg}$ to control.
   • Endogeneity: situations in which an explanatory variable is correlated with the error term.
     • When the independent and dependent variables are mutually causal, it leads to endogeneity. In a model, the variable whose value is determined by its relationship with other variables within the model, are endogenous; In contrast, exogenous variables are independent, which have no formulaic relationship.
     • In a model, the dependent variable should be endogenous, and independent variables should be exogenous, whose values not determined by the model. Endogeneity refers to the situation where explanatory variables are not entirely exogenous but exhibit endogeneity.

Main takeaway:

This paper examines gender peer effects on students’ academic and non-cognitive outcomes

• Higher proportion of female peers in class improves students’ test scores and noncognitive outcomes, which include their social acclimation and general satisfaction in school. ⇒10% increase in the proportion of female classmates raises students’ test scores by 10.2% of agi standard deviation and improves their social acclimation and satisfaction in school by 7.7% of a standard deviation.
• Heterogeneity of gender peer effects. ⇒ Positive effect on test score is stronger among male students, or when the teacher is male.
  • Heterogeneity: differences across the units being studied

Channels:

• More interactive teaching style, more time allocated to teaching-related tasks ⇒ when there are more female students in class, teachers tend to introduce more discussions with and among students, allocate more time to teaching and grading, and be more patient with and responsible for their students.
• Improved classroom environment ⇒Students also report that the environment is friendlier and more satisfying, and that they devote more hours to homework and tutorials.

Clarification: noncognitive outcome: mental stress, social acclimation and general satisfaction in school.
Caveats: No strong support for ability-based spillover from female students.