diff --git a/foqus_lib/gui/sdoe/sdoeAnalysisDialog.py b/foqus_lib/gui/sdoe/sdoeAnalysisDialog.py
index 573bc1f13..10855692d 100644
--- a/foqus_lib/gui/sdoe/sdoeAnalysisDialog.py
+++ b/foqus_lib/gui/sdoe/sdoeAnalysisDialog.py
@@ -178,10 +178,10 @@ def __init__(
             self.progress2_groupBox.setHidden(True)
 
         # spin box bounds
-        self.minDesignSize_spin.setMaximum(len(candidateData.getInputData()))
-        self.maxDesignSize_spin.setMaximum(len(candidateData.getInputData()))
-        self.designSize_spin.setMaximum(len(candidateData.getInputData()))
-        self.designSizeIRSF_spin.setMaximum(len(candidateData.getInputData()))
+        self.minDesignSize_spin.setMaximum(len(candidateData.getInputData()) - 1)
+        self.maxDesignSize_spin.setMaximum(len(candidateData.getInputData()) - 1)
+        self.designSize_spin.setMaximum(len(candidateData.getInputData()) - 1)
+        self.designSizeIRSF_spin.setMaximum(len(candidateData.getInputData()) - 1)
         self.ncand_samplesIRSF_spin.setRange(1, len(candidateData.getInputData()))
         self.ncand_samplesIRSF_spin.setValue(
             int(0.1 * len(candidateData.getInputData()))