I'm a bit confused as the output of my model in R.
I have built a generalised estimating equation glm model aiming to see the effect of time (here coded as timestrat) on a variable called new1804. I have controlled for a range of other variables.
mf04 <- formula(new1804 ~ timestrat + urban +
marital + ses + timeinsample+state +
dependancestrat + didattemptquitinlastyear +
plan2quit + agestrat + sex + weight23)
geeInd04 <- geeglm(mf04, id=uniqid,
data=finaldf04, family=poisson,
corstr="independence")
My confusion comes in the output of the model. ANOVA analysis says that timestrat is not significant. However, when looking at the summary- the coefficient and standard errors suggest that it is. I have calculated my upper and lower confidence interval for the coefficient as below and got the results of -0.2947138 for the lower bound and -0.0513192 for the upper bound.
If my 95% confidence interval for the coefficient is negative for both the upper and lower bound, why is it that ANOVA is returning a non significant result?
Calculation of upper and lower bounds:
lwrcoef <- estimate - 1.96*stderr
uprcoef <- estimate + 1.96*stderr
Summary of model:
Summary(geeInd04)
Call:
geeglm(formula = mf04, family = poisson,
data = finaldf04, id = uniqid,
corstr = "independence")
Coefficients:
Estimate Std.err Wald Pr(>|W|)
(Intercept) 0.70201 0.11849 35.10 3.1e-09 ***
timestrat1 -0.17302 0.06209 7.76 0.0053 **
urban2 -0.01993 0.04376 0.21 0.6488
marital2 -0.09071 0.08561 1.12 0.2893
marital3 0.01912 0.03451 0.31 0.5797
marital4 -0.05872 0.03356 3.06 0.0802 .
sesL -0.02625 0.02529 1.08 0.2994
timeinsample 0.09883 0.04358 5.14 0.0233 *
state19 0.03256 0.08025 0.16 0.6849
state23 0.15694 0.05939 6.98 0.0082 **
state27 0.10763 0.06275 2.94 0.0863 .
dependancestrat0 -0.00335 0.06022 0.00 0.9556
dependancestrat1 -0.02140 0.04915 0.19 0.6633
dependancestrat2 -0.02250 0.04619 0.24 0.6261
dependancestrat3 -0.07338 0.04452 2.72 0.0993 .
didattemptquitinlastyear1 -0.02050 0.03104 0.44 0.5090
plan2quit2 0.16451 0.06616 6.18 0.0129 *
plan2quit3 0.08602 0.06958 1.53 0.2163
plan2quit4 0.04591 0.06912 0.44 0.5066
agestrat40-55 0.00398 0.02541 0.02 0.8756
agestratOver 55 -0.05170 0.03324 2.42 0.1199
agestratUnder 30 0.03823 0.03150 1.47 0.2249
sex2 0.07681 0.02360 10.59 0.0011 **
weight23 0.04968 0.02310 4.63 0.0315 *
Signif. codes: 0 ‘*’ 0.001 ‘’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Correlation structure = independence
Estimated Scale Parameters:
Estimate Std.err
(Intercept) 0.454 0.0228
Number of clusters: 270 Maximum cluster
size: 99
Anova:
anova(geeInd04)
Analysis of 'Wald statistic' Table
Model: poisson, link: log
Response: new1804
Terms added sequentially (first to last)
Df X2 P(>|Chi|)
timestrat 1 1.79 0.18109
urban 1 0.21 0.64487
marital 3 2.98 0.39431
ses 1 0.82 0.36383
timeinsample 1 3.75 0.05273 .
state 3 7.45 0.05885 .
dependancestrat 4 4.41 0.35280
didattemptquitinlastyear 1 0.02 0.89898
plan2quit 3 15.87 0.00120 **
agestrat 3 8.80 0.03211 *
sex 1 10.95 0.00094 ***
weight23 1 4.63 0.03150 *
Signif. codes: 0 ‘*’ 0.001 ‘’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
> summary
function (object, ...)
UseMethod("summary")
<bytecode: 0x7fab49a332b0>
<environment: namespace:base>
> summary(geeInd04)
anovasaysTerms added sequentially (first to last). The other function is testing in the presence of all other variables. – user2554330 Apr 01 '22 at 16:54anova(). The documentation ingeepackdoesn't seem very clear about just whatanova()method it invokes for its models, or whether you could use something other than this default "Type I" sequential ANOVA. – EdM Apr 01 '22 at 17:16