My clustered several variables into a model. this set below is one of them

Overall, 6 clusters including the data set below are created.

I chose 3 level meta analysis cause level 3 is proven to be preffered according to anova() comparison.

However, Tau2_2 in the data is extremely low almost 0 with 3 decimal. this is the same for all other clusters.

and the overall model.

My question is that is there any constraint that works? or is it possible outcome?

Call:

meta3(y = fisherz, v = v, cluster = id, x = cbind("dis", "review"),

data = KORdb, intercept.constraints = 0, model.name = "Modelpub")

95% confidence intervals: z statistic approximation

Coefficients:

Estimate Std.Error lbound ubound z value Pr(>|z|)

Slope_1 3.0175e-01 3.1594e+02 -6.1892e+02 6.1953e+02 0.0010 0.99924

Slope_2 3.0175e-01 3.1594e+02 -6.1892e+02 6.1953e+02 0.0010 0.99924

Tau2_2 9.9365e-11 1.0092e-02 -1.9779e-02 1.9779e-02 0.0000 1.00000

Tau2_3 3.9636e-02 1.5767e-02 8.7337e-03 7.0537e-02 2.5139 0.01194 *

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Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1