เปรียบเทียบวิธี

	Difference-in-Differences (DiD)	วิธีการตัวแปรเครื่องมือ (IV) สำหรับการอนุมานเชิงสาเหตุ
สาขาวิชา	เศรษฐมิติ	เศรษฐศาสตร์สุขภาพ
ตระกูล	Regression model	Process / pipeline
ปีกำเนิด	1994	1990s (modern applications)
ผู้ริเริ่ม	Card & Krueger (canonical 1994 application); Angrist & Pischke (textbook treatment)	Angrist & Pischke (applied econometrics); rooted in econometric theory
ประเภท	Causal inference / panel regression	Method
แหล่งต้นตำรับ	Angrist, J. D., & Pischke, J.-S. (2009). Mostly Harmless Econometrics: An Empiricist's Companion. Princeton University Press. ISBN: 978-0691120355	Angrist, J. D., & Pischke, J. S. (2009). Mostly Harmless Econometrics: An Empiricist's Companion. Princeton: Princeton University Press.
ชื่อเรียกอื่น	diff-in-diff, DiD, Farkların Farkı (Diff-in-Diff)	IV, two-stage least squares, TSLS, causal estimation
ที่เกี่ยวข้อง	5	3
สรุป	Difference-in-Differences is a causal-inference method that estimates the effect of an intervention by comparing how a treatment group and a control group change over time. Made famous by Card and Krueger's 1994 minimum-wage study and developed in Angrist and Pischke's Mostly Harmless Econometrics, it isolates the treatment effect as the difference between the two groups' before-after changes.	Instrumental variables (IV) is an econometric method to estimate causal effects when treatment or exposure is not randomly assigned and confounding is severe or unmeasured. IV relies on a third variable (instrument) that influences treatment but does not directly affect the outcome, allowing researchers to isolate the causal effect from the noise of confounding. Developed extensively in econometrics (Angrist & Pischke, 1990s–2000s), IV methods are increasingly used in health economics and health services research to leverage natural experiments and policy changes.