diff --git a/functions/fisher_exact.py b/functions/fisher_exact.py
new file mode 100644
index 0000000..fa9b85b
--- /dev/null
+++ b/functions/fisher_exact.py
@@ -0,0 +1,39 @@
+from scipy.stats import fisher_exact
+
+
+def fisher_excat_upper(
+    correct_pattern_count: int, number_of_pattern: int, p_threshold: float = 5.0 / 100.0
+) -> float | None:
+    error_pattern_count = int(number_of_pattern - correct_pattern_count)
+
+    bound = None
+    for u in range(0, correct_pattern_count):
+        z = int(error_pattern_count + u)
+        _, pvalue = fisher_exact(
+            [[correct_pattern_count, error_pattern_count], [number_of_pattern - z, z]],
+            alternative="greater",
+        )
+        if bool(pvalue > p_threshold) is False:
+            bound = u * 100.0 / number_of_pattern
+            break
+
+    return bound
+
+
+def fisher_excat_lower(
+    correct_pattern_count: int, number_of_pattern: int, p_threshold: float = 5.0 / 100.0
+) -> float | None:
+    error_pattern_count = int(number_of_pattern - correct_pattern_count)
+
+    bound = None
+    for u in range(0, error_pattern_count):
+        z = int(error_pattern_count - u)
+        _, pvalue = fisher_exact(
+            [[correct_pattern_count, error_pattern_count], [number_of_pattern - z, z]],
+            alternative="less",
+        )
+        if bool(pvalue > p_threshold) is False:
+            bound = u * 100.0 / number_of_pattern
+            break
+
+    return bound