wednesday, december 5 chi-square test of independence: two variables. summing up!

Wednesday, December 5

Chi-square Test of Independence: Two Variables.Summing up!

Chi-square Test of Independence

Are two nominal level variables related or independentfrom each other?

Is race related to SES, or are they independent?

15

32

1928 47

Lo

Hi

SES

White Black

Row n x Column n

Total n

The expected frequency of any given cell is

15

32

1928 47

(15x28)/47 (15x19)/47

(32x28)/47 (32x19)/47

8.94 6.06

19.06 12.94

15

32

1928 47

Lo

Hi

SES

White Black

12 3

16 16

15

32

1928 47

8.94 6.06

19.06 12.94

12 3

16 16

2 =(fo - fe)2

fe

r=1

r

c=1

c

Please calculate:

Bivariate Statistics

Nominal Ordinal Interval

Nominal 2 Rank-sum t-testKruskal-Wallis H ANOVA

Ordinal Spearman rs (rho)

Interval Pearson rRegression

Y

X

Who said this?

"The definition of insanity is doing the same thing over and over again and expecting different results".

Who said this?

"The definition of insanity is doing the same thing over and over again and expecting different results".

• I don’t like it because from a statistical point of view, it is insane to do the same thing over and over again and expect the same results!

• More to the point, the wisdom of statistics lies in understanding that repeating things some ways ends up with results that are more the same than others. Hmm. Think about this for a moment. Statistics allows one to understand the expected variability in results even when the same thing is done, as a function of σ and N.

Your turn!

• If I take a sample of N=1, why can’t I make inferences to the larger population from this sample?

Your turn!

• If I take a sample of N=1, why can’t I make inferences to the larger population from this sample? What does Guinness have to do with it?