Descriptive Stats Flashcards
What means population
Greek letters:
Mean u , variance (sigma squared)
Correlation p
What means sample
Roman
Mean X bar, variance S^2, correlation r
Statistical inference is
Used to take data we know and describe data we don’t know
How close is X bar to mean u, s^2 to sigma squared ect
What dose the covariance and correlation measure
The strength of the linear relationship between two random variables
A positive covariance / correlation …
Implies that x and y move in the same direction
A negative covariance / correlation…
Implies that x and y often move in the opposite direction
Central tendency
The way the data clusters around some central value
Dispersion
The way observations tend to spread out around some central value
What are measures of central tendency
The mean (or average)
X bar = sample mean
Mu . U = population mean
What is median
Middle value in ordered data - not impacted by large or small outliers
What is a measure of dispersion
The standard deviation measures the dispersion around the mean
Variance is ?
Variance is the square root of the standard deviation
