ECO 391 EXAM 1 QUESTIONS N ANSWERS 2025/2026

ECO 391: EXAM 1 QUESTIONS N
ANSWERS 2025/2026

The Mean - correct answer ✔✔average



Sample Mean symbol - correct answer ✔✔x̅



Population Mean Symbol - correct answer ✔✔μ



Sample Mean Formula - correct answer ✔✔The sample mean formula is:

x̄ = ( Σ xi ) / n



x̄ just stands for the "sample mean"

Σ means "add up"

xi "all of the x-values"

n means "the number of items in the sample"



Population Mean Formula - correct answer ✔✔μ = (Σ * X)/ N

where:

Σ means "the sum of."

X = all the individual items in the group.

N = the number of items in the group.



Median - correct answer ✔✔The middle number in a set of numbers that are listed in order

, Mode - correct answer ✔✔the most frequently occurring score(s) in a distribution



Which percentile will the median always fall into? - correct answer ✔✔the 50th percentile



the Weighted Mean - correct answer ✔✔the mean of a data set whose entries have varying
weights



Weighted Mean Formula - correct answer ✔✔x̄ = ∑ (w • x) / ∑w



the Range - correct answer ✔✔the difference between the highest and lowest scores in a
distribution



Variance - correct answer ✔✔the squared differences between each data value and the mean
(SD^2)



Variance formula (sample) - correct answer ✔✔s^2=∑(xi-x̄)^2/n-1



Variance Formula (population) - correct answer ✔✔Simga^2=∑(xi-x̄)^2/N



SD and Variance relationship - correct answer ✔✔SD = Variance^2



Coefficent of Variation (CV) - correct answer ✔✔indicates how large SD is in relation to the
mean



Covariance - correct answer ✔✔descriptive measure of the linear association between two
variables