####################################################

  First Bioassay problem with just one group.

####################################################

WEIGHT
  BY Cases .

LOGISTIC REGRESSION  Response
  /METHOD = ENTER LogDose
  /CRITERIA = PIN(.05) POUT(.10) ITERATE(20) CUT(.5) .


####################################################

  Second Bioassay problem with two groups.

####################################################.

WEIGHT
  BY Subjects .

USE ALL.
COMPUTE filter_$=(Gorup = 1).
VARIABLE LABEL filter_$ 'Gorup = 1 (FILTER)'.
VALUE LABELS filter_$  0 'Not Selected' 1 'Selected'.
FORMAT filter_$ (f1.0).
FILTER BY filter_$.
EXECUTE .

LOGISTIC REGRESSION  Respond
  /METHOD = ENTER LogDose
  /PRINT = ITER(1)
  /CRITERIA = PIN(.05) POUT(.10) ITERATE(20) CUT(.5) .

USE ALL.
COMPUTE filter_$=(Gorup = 2).
VARIABLE LABEL filter_$ 'Gorup = 2 (FILTER)'.
VALUE LABELS filter_$  0 'Not Selected' 1 'Selected'.
FORMAT filter_$ (f1.0).
FILTER BY filter_$.
EXECUTE .

LOGISTIC REGRESSION  Respond
  /METHOD = ENTER LogDose
  /PRINT = ITER(1)
  /CRITERIA = PIN(.05) POUT(.10) ITERATE(20) CUT(.5) .

USE ALL.
EXECUTE .

COMPUTE grp = Gorup - 1 .
EXECUTE .


LOGISTIC REGRESSION  Respond
  /METHOD = FSTEP(LR) LogDose grp
  /PRINT = ITER(1)
  /CRITERIA = PIN(.05) POUT(.10) ITERATE(20) CUT(.5) .


COMPUTE grpX = grp * logdose .
EXECUTE .

LOGISTIC REGRESSION  Respond
  /METHOD = FSTEP(LR) LogDose grp grpX
  /PRINT = ITER(1)
  /CRITERIA = PIN(.94) POUT(.95) ITERATE(20) CUT(.5) .