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Table 3 Logistic Regression Results, odds ratios comparing likelihood of response.

From: Shortening a survey and using alternative forms of prenotification: Impact on response rate and quality

Variable OR 95% CI P-value
Main effects only     
   Notify: Postcard vs. Letter 1.04 0.77 1.39 0.80
   Pages: 2 vs 4 0.81 0.60 1.09 0.16
   Age: 1 year increase 1.03 1.01 1.04 0.0001
   Sex: Female vs Male 1.86 1.38 2.50 <.0001
   Race: White vs non-white* 3.35 1.77 6.35 0.0002
   Race: White vs other/unknown 2.23 1.49 3.35 0.0001
Including interaction between survey length and age
   Notify: Postcard vs. Letter 1.05 0.78 1.42 0.73
   Pages: 2 vs 4 (for 25-year-olds) 0.34 0.19 0.62 0.0004
   Pages: 2 vs 4 (for 35-year-olds) 0.53 0.36 0.79 0.0015
   Pages: 2 vs 4 (for 45-year-olds) 0.84 0.62 1.13 0.25
   Pages: 2 vs 4 (for 55-year-olds) 1.32 0.87 2.00 0.19
   Sex: Female vs Male 1.86 1.38 2.50 <.0001
   Race: White vs non-white* 3.40 1.79 6.47 0.0002
   Race: White vs other/unknown 2.33 1.55 3.50 <.0001
  1. Notes: Age was modeled continuously, therefore, the significant interaction in the second model was summarized by calculating the odds ratios at select points across the age range. P-value for survey length-by-age interaction = 0.001. There was no significant interaction found between notification method and survey length (p = 0.25).
  2. * "Non-white" includes: American Indian/Alaskan Native, Black or African American, Native Hawaiian/Pacific Islander, and Asian.