[R-meta] Two questions about the subgroup analysis

[전경남]

Dear all,
 
I performed a subgropu analysis using the meta package.
The following are the results of the analysis.
I have two questions about the results.
 
1. Is there any option that I can see the results of significant testsings
about whether each effect size estimates for the two groups are zero or not ?
 
2. Why could I get the results only for between groups under the random model? 
As you see, under the fixed effect model, 
information about both between groups and within groups are provided.
 
Thank you for your help in advance!
 
Kyungnam Jeon
 
 
----- The results of analysis ------
 
Number of studies combined: k = 15
 
                        SMD            95%-CI    z  p-value
Fixed effect model   0.0993 [ 0.0317; 0.1670] 2.88   0.0040
Random effects model 0.1026 [-0.0407; 0.2458] 1.40   0.1605
Quantifying heterogeneity:  tau^2 = 0.0595; H = 2.07 [1.62; 2.66]; I^2 = 76.7% [61.8%; 85.8%]
 
Test of heterogeneity:
     Q d.f.  p-value
 60.18   14 < 0.0001
 
Results for subgroups (fixed effect model):
                 k     SMD            95%-CI     Q    tau^2   I^2
level = ele     10  0.1959 [ 0.1097; 0.2822] 40.71   0.0696 77.9%
level = second   5 -0.0544 [-0.1633; 0.0544]  6.99   0.0117 42.8%
 
Test for subgroup differences (fixed effect model):
                   Q d.f.  p-value
Between groups 12.48    1   0.0004
Within groups  47.69   13 < 0.0001
 
Results for subgroups (random effects model):
                 k     SMD            95%-CI     Q    tau^2   I^2
level = ele     10  0.1873 [-0.0018; 0.3764] 40.71   0.0696 77.9%
level = second   5 -0.0538 [-0.1990; 0.0915]  6.99   0.0117 42.8%
 
Test for subgroup differences (random effects model): 
 
                    Q d.f.  p-value
Between groups   3.93    1   0.0475
 
Details on meta-analytical method:
- Inverse variance method
- DerSimonian-Laird estimator for tau^2
- Hedges' g (bias corrected standardised mean difference)
 

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