diff --git a/package/samplers/moead/_elite_population_selection_strategy.py b/package/samplers/moead/_elite_population_selection_strategy.py
index 865b04d5..d6124438 100644
--- a/package/samplers/moead/_elite_population_selection_strategy.py
+++ b/package/samplers/moead/_elite_population_selection_strategy.py
@@ -1,8 +1,5 @@
 from __future__ import annotations
 
-from _scalar_aggregation_func import pbi
-from _scalar_aggregation_func import tchebycheff
-from _scalar_aggregation_func import weighted_sum
 import numpy as np
 from optuna import Study
 from optuna.study import StudyDirection
@@ -10,6 +7,9 @@
 from scipy.spatial import cKDTree
 from scipy.stats import qmc
 
+from ._scalar_aggregation_func import tchebycheff
+from ._scalar_aggregation_func import weighted_sum
+
 
 class MOEAdElitePopulationSelectionStrategy:
     def __init__(
@@ -26,8 +26,6 @@ def __init__(
 
         if scalar_aggregation_func == "tchebycheff":
             self._scalar_aggregation_func = tchebycheff
-        elif scalar_aggregation_func == "PBI":
-            self._scalar_aggregation_func = pbi
         elif scalar_aggregation_func == "weighted_sum":
             self._scalar_aggregation_func = weighted_sum
         else:
diff --git a/package/samplers/moead/_scalar_aggregation_func.py b/package/samplers/moead/_scalar_aggregation_func.py
index 4f627c1e..6c13dab6 100644
--- a/package/samplers/moead/_scalar_aggregation_func.py
+++ b/package/samplers/moead/_scalar_aggregation_func.py
@@ -26,18 +26,3 @@ def tchebycheff(
     ref = np.array(reference_point)
     nadir = np.array(nadir_point)
     return float(np.max(lambda_ * np.abs((value - ref) / (nadir - ref))))
-
-
-# TODO: Is this method correct?
-def pbi(
-    weight_vector: list[float],
-    trial: FrozenTrial,
-    reference_point: list[float],
-    nadir_point: list[float],
-    theta: float = 5.0,
-) -> float:
-    diff = trial.values - reference_point
-    d1 = np.dot(diff, weight_vector)
-    d2 = np.linalg.norm(diff - d1 * weight_vector)
-
-    return d1 + theta * d2
diff --git a/package/samplers/moead/moead.py b/package/samplers/moead/moead.py
index 0cbc2999..5925bb09 100644
--- a/package/samplers/moead/moead.py
+++ b/package/samplers/moead/moead.py
@@ -6,8 +6,6 @@
 from typing import Dict
 from typing import TYPE_CHECKING
 
-from _child_generation_strategy import MOEAdChildGenerationStrategy
-from _elite_population_selection_strategy import MOEAdElitePopulationSelectionStrategy
 import optuna
 from optuna.distributions import BaseDistribution
 from optuna.samplers import BaseSampler
@@ -18,6 +16,9 @@
 from optuna.search_space import IntersectionSearchSpace
 from optuna.trial import FrozenTrial
 
+from ._child_generation_strategy import MOEAdChildGenerationStrategy
+from ._elite_population_selection_strategy import MOEAdElitePopulationSelectionStrategy
+
 
 if TYPE_CHECKING:
     from optuna.study import Study