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. 2019 Dec 6;21(12):e14475. doi: 10.2196/14475

Table 3.

Results of the meta-regression analyses of the design characteristics.

Design characteristics k Estimate SE P value 95% CI QM test (df) R² (%)







Study Group
Compliance
  Evaluations 104



—a 19 0
    Intercept
86.23 2.75
80.84-91.61


    Beta
−0.99 0.38 <.01 −1.73 to −0.25


  Days 103



— 1 0
    Intercept
78.69 1.86
75.04-82.34


    Beta
0.14 0.18 .43 −0.21 to 0.49


  Hours/day 76



— 36 0
    Intercept
74.8 10.41
54.39-95.21


    Beta
0.28 0.76 .71 −1.21 to 1.78


  Duration between evaluations 71



— 51 0
    Intercept
71.43 3.4
64.76-78.10


    Beta
0.06 0.02 .02 0.01-0.11


  Items 83



— 0 0
    Intercept
81.96 2.39
77.27-86.65


    Beta
−0.15 0.1 .14 −0.34 to 0.05


  Sampling scheme 103



6.78 22 0
    Intercept (semirandom)
78.5 1.64
75.27-81.72


    Beta (random)
−0.63 2.29 .78 −5.13 to 3.86


    Beta (fixed)
6.7 2.95 .02 0.90-12.50


  Data collection method 105



14.98 27 0
    Intercept (PDAb)
81.14 1.38
78.45-83.84


    Beta (paper-pencil)
−2.90 2.24 .20 −7.29 to 1.49


    Beta (calls)
6.89 4.75 .15 −2.43 to 16.20


    Beta (SMS)
−0.91 6.06 .88 −12.79 to 10.97


    Beta (voicemail)
−12.64 8.19 .12 −28.69 to 3.41


    Beta (Web-based)
−13.99 6.49 .03 −26.70 to −1.27


    Beta (mixed)
−16.5 7.79 .03 −31.77 to −1.23


  Scale type 102



0.28c 7 0
    Intercept (LSd)
79.03 1.45
76.19-81.87


    Beta (VASe)
−0.84 3.45 .81 −7.60 to 5.93


    Beta (mixed)
0.98 2.48 .69 −3.87 to 5.83


  Incentives 43



— 23 0
    Intercept
75.36 2.23   70.99-79.73


    Beta
0.04 0.02 .02 0.01-0.09


Retention
  Evaluations 111




0 1
    Intercept
1.275 0.053
1.171-1.379


    Beta
0.007 0.007 .34 −0.007 to 0.020


  Days 109



— 0 0
    Intercept
1.329 0.036
1.259-1.399


    Beta
−0.000 0.004 .96 0.007-0.007


  Hours/day 87



—

    Intercept
1.358 0.186
0.994-1.722


    Beta
−0.001 0.014 .92 −0.028 to 0.025


  Duration between evaluations 86



— 2 17
    Intercept
1.36 0.06
1.243-1.478


    Beta
−0.000 0 .71 −0.001 to 0.001


  Items 92



— 0 2
    Intercept
1.274 0.044
1.188-1.360


    Beta
0.002 0.002 .35 −0.00 to 0.01


  Sampling scheme 111



0.17c 0 0
    Intercept (semirandom)
1.322 0.031
1.263-1.382


    Beta (random)
−0.007 0.045 .88 −0.095 to 0.082


    Beta (fixed)
0.018 0.058 .76 −0.095 to 0.131


  Data collection method 112



7.22c 7 0
    Intercept (PDA)
1.342 0.026
1.291-1.393


    Beta (paper-pencil)
−0.039 0.043 .36 −0.124 to 0.046


    Beta (calls)
−0.123 0.114 .28 −0.346 to 0.101


    Beta (SMS)
0.082 0.121 .50 −0.155 to 0.318


    Beta (Web-based)
−0.153 0.089 .09 −0.328 to 0.022


    Beta (mixed)
0.229 0.164 .16 −0.093 to 0.550


  Scale type 111



1.55c 0 0
    Intercept (LS)
1.3 0.026
1.248-1.352


    Beta (VAS)
0.062 0.07 .37 −0.074 to 0.198


    Beta (mixed)
0.047 0.045 .30 −0.042 to 0.135


  Incentives 52



— 0 19
    Intercept
1.272 0.041
1.193-1.352


    Beta
0 0 .62 −0.001 to 0.001


aData not applicable.

bPDA: personal digital assistant.

cNot significant.

dLS: Likert scale.

eVAS: visual analogue scale.