diff --git a/Error Analysis in Experimental Physical Science.pdf b/Error Analysis/Error Analysis in Experimental Physical Science.pdf
similarity index 100%
rename from Error Analysis in Experimental Physical Science.pdf
rename to Error Analysis/Error Analysis in Experimental Physical Science.pdf
diff --git a/Error Analysis/Practice b/Error Analysis/Practice
new file mode 100644
index 0000000..eb47a5a
--- /dev/null
+++ b/Error Analysis/Practice	
@@ -0,0 +1,5 @@
+1)	a)	9 ± 2.24, 9 ± 24.9%
+	b)	1 ± 2.24, 1 ± 224%
+	c)	15 ± 2.24, 15 ± 14.9%;  if c had no error, then it comes to ± 2.2360, so I would still round that to ± 2.24
+
+2)	120
\ No newline at end of file
diff --git a/Error Analysis/error propagation b/Error Analysis/error propagation
new file mode 100644
index 0000000..fa08206
--- /dev/null
+++ b/Error Analysis/error propagation	
@@ -0,0 +1,22 @@
+Z = X + Y OR Z = X - Y
+      _________
+ΔZ = √ΔX² + ΔY²
+
+
+Z = X * Y OR Z = X / Y
+       __________________
+_ΔZ_ = / ⎛_ΔX_⎞² + ⎛_ΔY_⎞²
+  Z   √  ⎝  X ⎠    ⎝  Y ⎠
+
+
+Z = Xⁿ
+
+ΔZ = n X⁽ⁿ⁻¹⁾ ΔX, i.e. _ΔZ_ = n _ΔX_
+                        Z        X
+
+
+Z = 𝑓(X,Y,...)
+
+ΔZ² = ⎛_∂f(X,Y)_ ΔX⎞² +  ⎛_∂f(X,Y)_ ΔY⎞² + ... 
+      ⎝   ∂X       ⎠     ⎝   ∂Y       ⎠
+
diff --git a/error_analysis b/error_analysis
deleted file mode 100644
index 0e97f5c..0000000
--- a/error_analysis
+++ /dev/null
@@ -1,5 +0,0 @@
-1)	a)	9 ± 3, 9 ± 33%
-	b)	1 ± 3, 1 ± 300%
-	c)	15 ± 3.2, 15 ± 21.3%;  if c had no error, then, 15 ± 3, 15 ± 20%
-
-2)	
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