Midterm

Question 1

Types of Data (define each) - how’s the data collected?

Answer 1

Time Series, Cross-Section, Panel/Longitudinal

Question 2

Stochastic Variable

Answer 2

Random variable

Question 3

Types of data values (define each)

Answer 3

Cardinal (well-defined distances in between numbers)
Ordinal (not well-defined in between numbers)
Nominal (categorical)

Question 4

Difference between Greek variables and English letters (in most cases)

Answer 4

Greek variables are unknowns. English ones are known data

Question 5

Scalars vs. Random Variables

Answer 5

Scalars are real numbers, usually notated with lower case.
Random variables map events to real numbers, notated with upper case

Question 6

What’s E(X) defined as?

Answer 6

A weighted sum. Sum of xf(x) for discrete. Integral of xf(x) for continuous

Question 7

What’s sum of f(x)?

Answer 7

1

Question 8

Predicted Yhat sample regression equation

Answer 8

Yhat = B0hat+B1hat*Xi

Question 9

Sample Regression Function

Answer 9

Yi=B₀hat+B₁hat*Xi+ehat

Question 10

Validity, Internal Validity, External Validity

Answer 10

What extent are we measuring the actual concept?
Internal Validity = measuring actual concept in the sample
External validity = measurement is representative to a general setting

Question 11

Why 0 sum of residuals if passing through center?

Answer 11

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