GMAT数学辅导：算术知识点全解析(标准方差)
<p> <span word="GMAT">GMAT</span>数学辅导：算术知识点全解析</p><p> 5.标准方差：</p><p> <span word="One">One</span> <span word="of">of</span> <span word="the">the</span> <span word="most">most</span> <span word="common">common</span> <span word="measures">measures</span> <span word="of">of</span> <span word="dispersion">dispersion</span> <span word="is">is</span> <span word="the">the</span> <span word="standard">standard</span> <span word="deviation">deviation</span>. <span word="Generally">Generally</span> <span word="speaking">speaking</span>, <span word="the">the</span> <span word="greater">greater</span> <span word="the">the</span> <span word="data">data</span> <span word="are">are</span> <span word="spread">spread</span> <span word="away">away</span> <span word="from">from</span> <span word="the">the</span> <span word="mean">mean</span>, <span word="the">the</span> <span word="greater">greater</span> <span word="the">the</span> <span word="standard">standard</span> <span word="deviation">deviation</span>. <span word="The">The</span> <span word="standard">standard</span> <span word="deviation">deviation</span> <span word="of">of</span> <span word="n">n</span> <span word="numbers">numbers</span> <span word="can">can</span> <span word="be">be</span> <span word="calculated">calculated</span> <span word="as">as</span> <span word="follows">follows</span>:</p><p> <span word="find">find</span> <span word="the">the</span> <span word="arithmetic">arithmetic</span> <span word="mean">mean</span> ;</p><p> <span word="find">find</span> <span word="the">the</span> <span word="differences">differences</span> <span word="between">between</span> <span word="the">the</span> <span word="mean">mean</span> <span word="and">and</span> <span word="each">each</span> <span word="of">of</span> <span word="the">the</span> <span word="n">n</span> <span word="numbers">numbers</span> ;</p><p> <span word="square">square</span> <span word="each">each</span> <span word="of">of</span> <span word="the">the</span> <span word="differences">differences</span> ;</p><p> <span word="find">find</span> <span word="the">the</span> <span word="average">average</span> <span word="of">of</span> <span word="the">the</span> <span word="squared">squared</span> <span word="differences">differences</span> ;</p><p> <span word="take">take</span> <span word="the">the</span> <span word="nonnegative">nonnegative</span> <span word="square">square</span> <span word="root">root</span> <span word="of">of</span> <span word="this">this</span> <span word="average">average</span>.</p><p> <span word="Notice">Notice</span> <span word="that">that</span> <span word="the">the</span> <span word="standard">standard</span> <span word="deviation">deviation</span> <span word="depends">depends</span> <span word="on">on</span> <span word="every">every</span> <span word="data">data</span> <span word="value">value</span>, <span word="although">although</span> <span word="it">it</span> <span word="depends">depends</span> <span word="most">most</span> <span word="on">on</span> <span word="values">values</span> <span word="that">that</span> <span word="are">are</span> <span word="farthest">farthest</span> <span word="from">from</span> <span word="the">the</span> <span word="mean">mean</span>. <span word="This">This</span> <span word="is">is</span> <span word="why">why</span> <span word="a">a</span> <span word="distribution">distribution</span> <span word="with">with</span> <span word="data">data</span> <span word="grouped">grouped</span> <span word="closely">closely</span> <span word="around">around</span> <span word="the">the</span> <span word="mean">mean</span> <span word="will">will</span> <span word="have">have</span> <span word="a">a</span> <span word="smaller">smaller</span> <span word="standard">standard</span> <span word="deviation">deviation</span> <span word="than">than</span> <span word="data">data</span> <span word="spread">spread</span> <span word="far">far</span> <span word="from">from</span> <span word="the">the</span> <span word="mean">mean</span>.</p><p> </p>
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