ANOVA with weights

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nbaydar
Posts: 1
Joined: Thu Sep 11, 2008 11:13 am

ANOVA with weights

Postby nbaydar » Thu Sep 11, 2008 11:38 am

I need to conduct an ANOVA with a weighted sample for meta analyses. I am attaching a very simple example where I tried the ANOVA in three different ways:

(1) Means procedure
(2) One-way ANOVA
(3) GLM UNIANOVA

All three procedures give three different sets of results if the cases are weighted. Furthermore, all of these differ from the results that I get by using REGWGT option in UNIANOVA. In conclusion, I have four different sets of results for what I thought would yield a unique result. If the cases are not weighted, the three procedures listed above give exactly the same results. I have two questions:
(1) Why are the results different?
(2) Which are the correct results?

I am attaching a syntax. I can also send data and output using regular email. Data are very simple - just 14 cases. The independent variable has only 2 categories (0 and 1). By the way, t-test gives yet a different set of results.

**********************************************************.
*************** UNWEIGHTED.
MEANS
TABLES=es_max BY parents
/CELLS MEAN COUNT STDDEV
/STATISTICS ANOVA .
ONEWAY
es_max BY parents
/STATISTICS DESCRIPTIVES
/MISSING ANALYSIS .
UNIANOVA
es_max BY parents
/METHOD = SSTYPE(3)
/INTERCEPT = INCLUDE
/EMMEANS = TABLES(parents)
/PRINT = DESCRIPTIVE
/CRITERIA = ALPHA(.05)
/DESIGN = parents .

**********************************************************.
*************** WEIGHTED.
WEIGHT
BY w_now .
DESCRIPTIVES
VARIABLES=es_max
/STATISTICS=MEAN STDDEV MIN MAX .
FREQUENCIES
VARIABLES=parents
/ORDER= ANALYSIS .
MEANS
TABLES=es_max BY parents
/CELLS MEAN COUNT STDDEV
/STATISTICS ANOVA .
ONEWAY
es_max BY parents
/STATISTICS DESCRIPTIVES
/MISSING ANALYSIS .
UNIANOVA
es_max BY parents
/METHOD = SSTYPE(3)
/INTERCEPT = INCLUDE
/EMMEANS = TABLES(parents)
/PRINT = DESCRIPTIVE
/CRITERIA = ALPHA(.05)
/DESIGN = parents .

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