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Table 1 Descriptive statistics

From: The time-varying role of the family in student time use and achievement

Sample Full Matched Sibling-pair
Student-year observations 5,896,480 3,781,981 1,241,126
Unique students 1,832,309 1,088,628 524,792
Unique schools 2144 2144 2141
Match rate to birth data 0.641  
Unique mothers    696,632 226,562
Math score (std devs) 0 (1) −0.012 (0.988) −0.026 (1.008)
Reading score (std devs) 0 (1) −0.014 (0.989) −0.061 (1.008)
Homework (std devs) 0 (1) −0.013 (0.989) −0.028 (0.988)
Free reading (std devs) 0 (1) −0.048 (0.969) −0.058 (0.968)
Computer use (std devs) 0 (1) −0.027 (0.974) −0.036 (0.965)
TV watching (std devs) 0 (1) 0.023 (1.003) 0.009 (1.015)
Homework (h/week) 2.41 (2.37) 2.39 (2.35) 2.35 (2.34)
Free reading (h/day) 0.80 (0.63) 0.77 (0.61) 0.77 (0.60)
Computer use (days/month) 3.01 (5.90) 2.84 (5.73) 2.80 (5.69)
TV watching (h/day) 2.51 (1.99) 2.56 (2.00) 2.53 (2.02)
White 0.558   0.600   0.595  
Black 0.276   0.293   0.305  
Hispanic 0.097   0.050   0.039  
Other race 0.037   0.029   0.031  
Multiracial 0.031   0.028   0.029  
Female 0.493   0.494   0.495  
Subsidized lunch 0.448   0.437   0.512  
Mother education    12.6 (2.5) 12.6 (2.5)
Mother age    26.0 (5.9) 25.4 (5.6)
Mother married    0.656   0.661  
Mother immigrant    0.072   0.057  
No father information    0.137   0.146  
Father education    12.7 (2.5) 12.8 (2.5)
Father age    29.0 (6.6) 28.6 (6.3)
Father immigrant    0.085   0.074  
First born    0.437   0.323  
Birth weight    7.29 (1.31) 7.21 (1.38)
Alcohol when pregnant    0.012   0.012  
Tobacco when pregnant    0.172   0.172  
  1. Sources: North Carolina Education Research Data Center and North Carolina State Center for Health Statistics. Sample: Students in grades 4–8, years 2003–2013. Standard deviations in parentheses