Dear all:
I am stuck with a problem in pearson chi-square test with survey
command. I have setup survey setting for Nationwide Inpatient Survey
(NIS) data. I used hospital id as sampling unit, discwt as sampling
weight and stratum variable as strata as suggested on NIS website.
When I am trying to run chi-square test for independence between age
category and year of data collection from 1998 to 2007, it gives
proper result, but when I run the same command by retaining only two
years (1998 and 2007), it does not produce p-value. I don't understand
why it is happening? Can anybody help me - what I should do? I am also
getting similar results with other variables that same command works
with more year but doesn't work with two years.
I have pasted my output for your ready reference.
Thanking you in advance,
Mihir
svyset hospid [pweight=discwt], strata(stratum) vce(linearized)
pweight: discwt
VCE: linearized
Strata 1: stratum
SU 1: hospid
FPC 1: <zero>
svy: tabulate year age2cat, count column row obs percent format(%10.0g) pearson
(running tabulate on estimation sample)
Number of strata = 60 Number of obs = 157222
Number of PSUs = 3270 Population size = 759816.12
Design df = 3210
-------------------------------------------
| age2cat
YEAR | <65 year >=65 yea Total
----------+--------------------------------
1998 | 27548.394 10497.654 38046.048
| 72.408029 27.591971 100
| 4.9658285 5.1193873 5.0072705
| 5452 2102 7554
|
1999 | 25591.467 9586.1825 35177.649
| 72.749224 27.250776 100
| 4.613076 4.6748901 4.6297582
| 5265 1991 7256
|
2000 | 25067.72 9839.9109 34907.631
| 71.811576 28.188424 100
| 4.5186663 4.7986258 4.5942209
| 5163 2032 7195
|
2001 | 24673.646 9882.7968 34556.443
| 71.401001 28.598999 100
| 4.4476311 4.8195399 4.5480007
| 4983 1976 6959
|
2002 | 83751.067 30869.413 114620.48
| 73.068152 26.931848 100
| 15.096831 15.054075 15.085292
| 17682 6513 24195
|
2003 | 80686.437 27375.013 108061.45
| 74.66718 25.33282 100
| 14.544405 13.349963 14.222053
| 17002 5737 22739
|
2004 | 77406.999 26898.738 104305.74
| 74.211641 25.788359 100
| 13.953259 13.117698 13.72776
| 16052 5540 21592
|
2005 | 74552.231 27032.143 101584.37
| 73.389467 26.610533 100
| 13.438663 13.182755 13.3696
| 15263 5507 20770
|
2006 | 68720.522 26875.807 95596.329
| 71.886152 28.113848 100
| 12.387449 13.106515 12.581508
| 14234 5538 19772
|
2007 | 66760.785 26199.193 92959.979
| 71.816696 28.183304 100
| 12.03419 12.776551 12.234536
| 13813 5377 19190
|
Total | 554759.27 205056.85 759816.12
| 73.012306 26.987694 100
| 100 100 100
| 114909 42313 157222
-------------------------------------------
Key: weighted counts
row percentages
column percentages
number of observations
Pearson:
Uncorrected chi2(9) = 91.4953
Design-based F(7.98, 25611.84)= 3.0966 P = 0.0017
keep if year==1998|year==2007
svy: tabulate year age2cat, count column row obs percent format(%10.0g) pearson
(running tabulate on estimation sample)
Number of strata = 60 Number of obs = 26744
Number of PSUs = 1205 Population size = 131006.03
Design df = 1145
-------------------------------------------
| age2cat
YEAR | <65 year >=65 yea Total
----------+--------------------------------
1998 | 27548.394 10497.654 38046.048
| 72.408029 27.591971 100
| 29.210724 28.60642 29.041449
| 5452 2102 7554
|
2007 | 66760.785 26199.193 92959.979
| 71.816696 28.183304 100
| 70.789276 71.39358 70.958551
| 13813 5377 19190
|
Total | 94309.179 36696.848 131006.03
| 71.988428 28.011572 100
| 100 100 100
| 19265 7479 26744
-------------------------------------------
Key: weighted counts
row percentages
column percentages
number of observations
Pearson:
Uncorrected chi2(1) = 0.9557
Design-based F(., .) = . P = .
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
