1: Descriptive Statistics

Question 1

Time series data

Answer 1

observations on the values a variable takes over time. for example, quarterly GDP

Question 2

cross-sectional data

Answer 2

data of individuals, households, firms, cities, states, countries, or other units of interest at a specific point in time.
obtained from random sampling of underlying population
for example, class results on a certain test

Question 3

panel data

Answer 3

the same cross-sectional units are followed over time
used to model lagged responses

Question 4

pooled cross sections

Answer 4

data configuration where independent cross sections, usually collected at different points in time, are combined to form a single data set

Question 5

positive skewness

Answer 5

there are positive outliers, positive extreme values

Question 6

negative skewness

Answer 6

there are negative outliers, negative extreme values

Question 7

positive kurtosis

Answer 7

more peaked than normal
there are more observations around the mean

Question 8

negative kurtosis

Answer 8

less peaked than normal
observations are more evenly spread

Question 9

zero kurtosis

Answer 9

equivalent to the normal distribution

Question 10

skewness formula

Answer 10

=((1/(N−1)) ∑▒(y_i−y ̅ )^3 )/((σ^2 )^(3/2) )

Question 11

kurtosis formula

Answer 11

=((1/(N−1)) ∑▒(y_i−y ̅ )^4 )/((σ^2 )^2 )

Question 12

correlation and covariance

Answer 12

measure the extent to which two variables move together
covariance has units
correlation has no units and ranges from -1 to 1