SQL - Statistics normal distribution amount range
<p>I have a <code>SQL Server</code> Database table with about 100K records of invoices (date, provider, type and amount).</p>

<p>This is sample data:</p>

<p><a href="https://i.stack.imgur.com/J9IdX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/J9IdX.png" alt="enter image description here"></a></p>

<p>I want to group my data into 4 segments depending on the amount.</p>

<ol>
<li>Group 1: &lt; X1</li>
<li>Group 2: Between X1 &amp; X2</li>
<li>Group 3: Between X2 &amp; X3</li>
<li>Group 4: > X3</li>
</ol>

<blockquote>
  <p>Where X1, X2 and X3 are amounts, but these amounts should be calculated statistically based on normal distribution so they make sense.</p>
</blockquote>

<p>So I guess I have to get my AVG(amount) and my STDEV(amount) in order to know what my X1, X2 and X3 values should be acceptable.</p>

<p>Any clue on how to do this so the values makes sense for a report so I can generate a chart like this:</p>

<p><a href="https://i.stack.imgur.com/MeEiq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MeEiq.png" alt="enter image description here"></a></p>