dod_fit  R Documentation 
Fits the Thurstonian DegreeofDifference (DOD) model.
This function is for programming use. The ordinary user probably wants
the dod
function, which is for interactive use.
dod_fit
only estimates the DOD model and performs no hypothesis
or significance tests.
dod_fit(same, diff, tau=NULL, d.prime=NULL, control=dodControl(),
...)
same 
the answers to samepairs; either 1) a numeric vector of counts of length equal to the number of response categories ordered appropriately or 2) a factor where the levels indicate the response categories. 
diff 
the answers to differentpairs in the same format as

tau 
optional vector of boundary parameters. If specified,

d.prime 
optional dprime value. If specified,

control 
options to control the fitting process specfied via a
call to 
... 
not currently used. 
The standard error of dprime is not defined when the parameter
estimate is zero (or numerically close) and it will be reported as
NA
in this case.
An object of class dod_fit
.
Rune Haubo B Christensen
dod
,
dodSim
, optimal_tau
,
dodPwr
,
dodControl
## DOD example data:
same.pairs < c(25, 22, 33, 20)
diff.pairs < c(18, 22, 30, 30)
## Fit Thurstonian dodmodel and perform difference test:
fm < dod_fit(same=same.pairs, diff=diff.pairs)
names(fm)
## Estimate dprime for given tau:
fm < dod_fit(same=same.pairs, diff=diff.pairs, tau=1:3)
## Estimate tau for given dprime:
fm < dod_fit(same=same.pairs, diff=diff.pairs, d.prime=1)
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