e</span><span class="w"> </span><span class="nv">mean</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">(</span><span class="nv">sum</span><span class="w"> </span><span class="nv">of</span><span class="w"> </span><span class="nv">the</span><span class="w"> </span><span class="nv">observations</span><span class="ss">)</span><span class="o">/</span><span class="nv">n</span>.

<span class="k">For</span><span class="w"> </span><span class="nv">a</span><span class="w"