Fix broken links/incorrect variance calculation (apple#422)

Author: natecook1000

Examples/math/Math.swift

@@ -176,7 +176,7 @@ extension Math.Statistics {
                 let squaredErrors = values
                     .map { $0 - mean }
                     .map { $0 * $0 }
-                let variance = squaredErrors.reduce(0, +)
+                let variance = squaredErrors.reduce(0, +) / Double(values.count)
                 let result = variance.squareRoot()
                 print(result)
             }

README.md

@@ -81,9 +81,10 @@ For guides, articles, and API documentation see the
 
 This repository includes a few examples of using the library:
 
-- [`repeat`](Examples/repeat/main.swift) is the example shown above.
+- [`repeat`](Examples/repeat/Repeat.swift) is the example shown above.
 - [`roll`](Examples/roll/main.swift) is a simple utility implemented as a straight-line script.
-- [`math`](Examples/math/main.swift) is an annotated example of using nested commands and subcommands.
+- [`math`](Examples/math/Math.swift) is an annotated example of using nested commands and subcommands.
+- [`count-lines`](Examples/count-lines/CountLines.swift) uses `async`/`await` code in its implementation.
 
 You can also see examples of `ArgumentParser` adoption among Swift project tools:
 

Sources/ArgumentParser/Documentation.docc/Articles/CommandsAndSubcommands.md

@@ -164,7 +164,7 @@ extension Math.Statistics {
                 let squaredErrors = values
                     .map { $0 - mean }
                     .map { $0 * $0 }
-                let variance = squaredErrors.reduce(0, +)
+                let variance = squaredErrors.reduce(0, +) / Double(values.count)
                 let result = variance.squareRoot()
                 print(result)
             }