title: Excel and R give me different answer for first Quantile
body: <p>I have the following data set (<code>n = 20</code>).</p>
  <pre><code>35, 50, 50, 50, 60, 75, 75, 75, 80,85,85,90,90,100,100,100,100,125,125,150
  </code></pre>
  <p>I try to find the first quantile. I do it manually as follows:</p>
  <pre><code>(25 / 100) * 20 = 5.
  </code></pre>
  <p>That means, the average of the <code>5th</code> and the <code>6th</code> positions, as follows:</p>
  <pre><code>(60+75)/2 = 67.5
  </code></pre>
  <p>However, when I do it in excel or R, they gave me, <code>Q_1 = 71.25</code></p>
  <p>Could you please help me to understand the problem?</p>