Lecture #6 (Nonparametric Statistics) Flashcards
Why nonparametric statistics?
Some data is ordinal which isn’t distributed in a probability distrbution
What are nonparametric statistics?
Tests we can perform without cardinal (ratio/interval) data
Do nonparametric statistics generally accept greater or smaller differences to accept H0?
Greater
What is the Mann-Whitney U test?
The mann-whitney U test is used to compare two independent samples using summed ranks
What is H0 mean in the Mann-Whitney U test? What does H1 mean?
H0 = The two datasets are drawn from the same population H1 = The two datasets are drawn from different populations
How do you perform the rank sum?
Reorder data into smallest to largest. Assess an associated value of 1 to (n) in a table. Average the rank of the second column if there are values which repeat. Put new ranks as the values in the datasets and calculate the sum of each.
How do you find the U-stat of each rank sum?
U-stat = RANKSUM - n(n+1)
———
2
Use the lower value in the U-test
How do we determine if the U-stat is statically different?
The U-stat is equal or lower than the U-critical
How do you perform Chi Squared?
CBCC
1) CONSTRUCT a contingency table of all observed outcomes (frequency)
2) BUILD a table of “expected” outcomes
3) CALCULATE Chi Squared
4) COMPARE the calculated Chi squared value to the critical
value from the tables, or calculate the p value
What is the formula for Chi Squared?
x² = Σ ((Oᵢ - Eᵢ)² / Eᵢ)
In Chi Squared, what is the conclusion to the hypothesis if the critical value is greater than the calculated value?
We accept H₀
Can data be in percentages for Chi Squared?
No, data must be ordinal or nominal and must be actual counts
What is Chi Squared used for?
to examine the differences between categorical variables in the same population
What is the K-S test?
Similar to the Chi Squared test, however K-S uses categorized cardinal data.
