Table 1 Factorial ANOVA across preterm birth clusters. Asterisks reflect significance at a significance level of 0.001

Cluster

High-High

Low-Low

Low-High

High-Low

P-value

Counties per Cluster

795

952

201

187

Demographic Variable

Mean

SD

Mean

SD

Mean

SD

Mean

SD

Population

64496.61

196449.9

126214.1

280923.7

69071.4

140112.1

106369.1

252554.9

6.09E-07*

% White

72

20.86

89.12

10.51

83.49

13.68

86.84

15.03

9.04E-103*

% Black

22.68

20.48

3.12

5.34

10.52

12.53

4.47

7.67

1.40E-166*

% American Indian

0.83

5

1.12

3.04

0.62

1.26

3.35

12.27

1.97E-08*

% Asian

0.78

1.04

1.99

3.58

1.07

1.61

1.18

1.58

2.72E-21*

% Hispanic

6.51

12.41

7.83

9.97

8.43

12.45

7.56

8.57

0.04073

Median Household Income

44685.49

10668.47

60557.75

14883.34

50749.5

13795.23

54713.7

10114.64

3.72E-124*

% With SNAP Benefits in Past Year

17.55

6.56

9.85

4.5

13.62

5.53

11.49

5.22

2.63E-157*

% With Health Insurance

88.98

4.49

93.01

3.5

89.25

4.19

91.71

5.6

1.83E-87*

% With Public Health Insurance

43.65

8.58

37.17

8.36

40.37

9.13

38.73

7.59

6.85E-53*

% Families in Poverty

15.21

5.77

7.66

3.07

11.77

4.67

9.32

4.37

1.98E-212*

% Households: Married

47.41

7.25

51.96

5.66

51.98

6.02

49.85

6.39

6.67E-49*

% Households: Single Parent

6.25

2.48

3.81

1.38

4.78

1.91

4.47

1.74

1.74E-130*

% Births: Unmarried

44.31

20.3

29.41

14.9

34.19

19.67

37.7

16.94

1.82E-62*

% 25 + Year Old: Bachelor’s Degree or Beyond

17.28

7.12

26.09

10.6

21.12

10.63

21.71

6.45

2.55E-80*

% Households: Spanish Speaking

4.95

9.82

5.43

8.07

6.13

9.05

4.98

6.72

0.320591

Population Density

148.58

363.72

486.89

3125.64

172.81

333.32

357.03

1187.19

0.007615

2013 Rural Urban Cont. Code

4.99

2.57

4.79

2.75

4.82

2.75

5.17

2.7

0.215512