Panel-Regression-Quiz

Panel data combines both cross-sectional and time-series dimensions.

• Yes

• No

Answer explanation

Panel data follows multiple individuals (or countries, firms, etc.) across multiple time periods, combining both dimensions.

Which of the following best describes cross-sectional data?

• Repeated observations of the same units over time

• Data from many individuals observed only once

• A time series of one individual or country

• Randomly simulated data

Answer explanation

Cross-sectional data provides a snapshot at one point in time — e.g., income and education for many people in 2024.

In a panel dataset, what is the main advantage compared to pure cross-sectional data?

• It allows for larger sample sizes only

• It ignores unobserved heterogeneity

• It tracks the same units over time to study dynamics

• It removes the need for control variables

Answer explanation

Panel data lets us observe how variables change within the same units over time, helping to control for unobserved fixed characteristics.

Fixed effects models remove time-invariant differences across individuals (or countries, firms, etc.).

• Yes

• No

Answer explanation

Fixed effects control for all factors that don’t change over time within a unit (like geography or culture), so only within-unit variation matters.

Which of the following are true about omitted-variable bias in panel regressions?

• It occurs when unobserved factors influence both X and Y.

• Fixed effects help reduce bias from unobserved, time-invariant variables.

• It disappears automatically as sample size increases.

• It only affects cross-sectional data.

Answer explanation

If an unobserved variable affects both X and Y, the estimated effect of X is biased. Fixed effects models “subtract out” those constant unobserved factors.

In a fixed-effects model, the effect of X on Y is identified from:

• Differences between individuals

• Differences over time within the same individual

• Random assignment of X

• Cross-country averages

Answer explanation

Fixed effects rely on within-unit variation over time — how changes in X for a given unit correspond to changes in Y for that same unit.