Chi square Flashcards
parametrics stats assumptions
Sample is large enough
comes from normal distribution
homogeneity
What do we do when assumptions are not met?
Use non-parametric Statistics
Non-parametric Statistics
- distribution free
- allows to analyze different data
Chi-Square X2
allows to determine if what you observe in a distribution is what would be expected by chance alone
number of dimensions
one sample:majors
two sample: majors by class year
Given no other information you expect categories to be equal
examples of when to use chi square
Gambling–> is it fair
criminal justice–> are police in wichita engaging in social profiling?
chi-square equation
X2 = ∑ (O-E)2/ E
X2 = Test statistic
O = Observed Frequency
E = Expected Frequency (By chance)
computing chi square
Null and Research Hypothesis (Words and Symbols)
Compute the Test Statistic
Determine if it is significant or not
Write a 2-3 sentence results section, including a numerical X2 statement.
hypotheses
Null hypothesis
H0: P1 = P2 = P3
Research hypothesis
H1: P1 P2 P3
Chi Square Example
Is the distribution of answers different than we would expect by chance?
Null Hypothesis: The responses not different than expected by chance
Research Hypothesis: The responses are different than expected by chance, reflecting some underlying preference
questions to ask ourselves
What’s our research question?
What’s our null hypothesis?
What’s our research hypothesis?
Table steps
Category/ O/E/D/(O-E)2/(O-E)2/E
Presenting Your Results (example)
x2(2) = 20.6, p < .05 x2 represents the test statistic 2 is the number of degrees of freedom 20.6 is the obtained value p < .05 is the probability