Hello,
I am working with household-level income and expenditure data collected using a two-stage stratified sampling design, the strata being region (urban vs rural) and PSU.
I have ranked households into wealth quintiles using income (quintinc) and expenditure (quintexp) separately and want to assess how comparable these two methods are. Specifically, I want to see how good household expenditure is as a predictor for household income. I believe Kendall's Tau B is the best way to assess this as it can deal with ties (output below).
While the -ktau- command lets me do a Tau B test, I don't see option to specify sampling type, and am not sure how much the estimates will be affected by sampling type.
I found a similar post on here where someone recommended using -somersd- (output below).
However:
I am working with household-level income and expenditure data collected using a two-stage stratified sampling design, the strata being region (urban vs rural) and PSU.
I have ranked households into wealth quintiles using income (quintinc) and expenditure (quintexp) separately and want to assess how comparable these two methods are. Specifically, I want to see how good household expenditure is as a predictor for household income. I believe Kendall's Tau B is the best way to assess this as it can deal with ties (output below).
Code:
. ktau quintexp quintinc, stats(taub p) Number of obs = 24238 Kendall's tau-a = 0.4830 Kendall's tau-b = 0.6104 Kendall's score = 1.4e+08 SE of score = 1200861.722 (corrected for ties) Test of Ho: quintexp and quintinc are independent Prob > |z| = 0.0000 (continuity corrected)
I found a similar post on here where someone recommended using -somersd- (output below).
Code:
. somersd quintexp quintinc [pwei=weights], taua tdist transf(z) cluster(psu) wstrata(region) Kendall's tau-a with variable: quintexp Transformation: Fisher's z Within strata defined by: region Valid observations: 24238 Number of clusters: 1605 Degrees of freedom: 1604 Symmetric 95% CI for transformed Kendall's tau-a (Std. Err. adjusted for 1,605 clusters in psu) ------------------------------------------------------------------------------ | Jackknife quintexp | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- quintexp | 1.061161 .0046923 226.15 0.000 1.051957 1.070364 quintinc | .4812417 .0091699 52.48 0.000 .4632553 .499228 ------------------------------------------------------------------------------ Asymmetric 95% CI for untransformed Kendall's tau-a Tau_a Minimum Maximum quintexp .78610767 .78256598 .78959848 quintinc .44723747 .43273369 .4615098
However:
- I cannot use this to do a Tau B test. ("option taub not allowed")
- I'm not completely sure I understand how to interpret this output
- While I've read the help files, I don't understand what the tdist and transf(z) options are doing and if they're necessary here.
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