Browse Source

Add a confidence interval calculator

Samuel W. Flint 2 years ago
parent
commit
b4b83134c3
1 changed files with 60 additions and 0 deletions
  1. 60 0
      calc-ci

+ 60 - 0
calc-ci

@@ -0,0 +1,60 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i python3 -p python3 python3Packages.pandas python3Packages.numpy python3Packages.scipy python3Packages.pyarrow
+# coding: utf-8
+
+from scipy.integrate import quad
+import pandas as pd
+import numpy as np
+
+from pathlib import Path
+
+
+def normalProbabilityDensity(x):
+    constant = 1.0 / np.sqrt(2*np.pi)
+    return (constant * np.exp((-x**2) / 2.0))
+
+home = Path.home()
+snt_path = Path(home, ".standard-normal.csv")
+
+if snt_path.exists():
+    snt = pd.read_csv(snt_path, index_col=0)
+else:
+    snt = pd.DataFrame(data    = [],
+                       index   = np.round(np.arange(0, 3.5, 0.1), 2),
+                       columns = np.round(np.arange(0.00, 0.1, 0.01), 2))
+
+    for index in snt.index:
+        for column in snt.columns:
+            z = np.round(index + column, 2)
+            value, _ = quad(normalProbabilityDensity, np.NINF, z)
+            value = np.round(value - 0.5, 4)
+            snt.loc[index,column] = value
+    snt.to_csv(snt_path)
+
+def find_z(p):
+    posns = []
+    res = snt.isin([p])
+    srs = res.any()
+    cols = list(srs[srs == True].index)
+    for col in cols:
+        rows = list(res[col][res[col] == True].index)
+        for row in rows:
+            posns.append(float(col) + row)
+    return np.max(posns)
+
+mean = float(input("Sample Mean: "))
+std = float(input("Standard Deviation: "))
+N = int(input("Sample Size: "))
+alpha = float(input("Alpha [0, 1): "))
+alpha_2 = alpha / 2
+
+Z_alpha_2 = find_z(alpha_2)
+
+plus_minus = np.round(Z_alpha_2 * (std / np.sqrt(N)), 4)
+
+print(f"{mean} +/- {plus_minus}")
+print(f"[{mean - plus_minus}, {mean + plus_minus}]")
+
+### Local Variables:
+### mode: python
+### End: