Week 1 - Descriptive Statistics Flashcards
How do you calculate the Mean
Mean = Sum of x, divided by N
How do you calculate the Mean from a Frequency table
Mean = Sum of fx, divided by the sum of f
Which average do you use if the data is highly skewed, and why
The median, it is a non-parametric statistic (not affected by skewness)
What is the Mode
The most frequently occuring value in the sample, in grouped data it is the class interval with the greatest frequency
How can we measure the Dispersion of data
Range, Interquartile range, Variance, and Standard deviation
How do you calculate the Variance
v2 = sum of (x - mean)2 divided by N
How do you calculate the Standard deviation
SD = square root of v
How do you calculate the Sample Variance
s2 = sum of (x - sample mean)2 divided by n - 1
How do you calculate the Variance from a Frequency table
v2 = sum of f(x - mean)2 divided by sum of f
How do you calculate the Sample variance with Grouped data
s2 = sum of f(x - sample mean)2 divided by n - 1
What is the Coefficient of Variation
CV = SD divided by the mean
(the higher the CV, the greater the level of dispersion around the mean)
How do you identify Skewness
Symmetric (right and left tails are mirror images), Negatively skewed (left tail longer than right tail), Positively skewed (right tail longer than left tail)
How do you calculate Skewness
Skewness = sum of f(x - mean)3 divided by NSD3
What is Cross sectional data
Where observations are made at a single point in time
What is Time series data
Where observations on the same variable are taken repeatedly over time
