Stability of calculating student grades in PHP

This article mainly introduces to you the stability operation of PHP to calculate student scores based on variance and standard deviation, and involves the operation skills related to PHP mathematical operations. Friends who need it can refer to it. I hope it can help everyone.

The student side of the project has a personal growth profile module, which requires analyzing the student's performance stability through fluctuation collection based on the student's recent ten test scores. Anyone who has studied mathematics knows that this should be achieved using the variance in mathematics. Since I am a scumbag in mathematics, I had to read the relevant instructions and formulas online. See the picture below

Okay, now that you have the formula, it will be easy to do. Next It's just a formula.

$arr1 = array(50, 100, 100, 60, 50);
$arr2 = array(73, 70, 75, 72, 70);
function variance($arr) {
  $length = count($arr);
  if ($length == 0) {
    return array(0,0);
  }
  $average = array_sum($arr)/$length;
  $count = 0;
  foreach ($arr as $v) {
    $count += pow($average-$v, 2);
  }
  $variance = $count/$length;
  return array('variance' => $variance, 'square' => sqrt($variance), 'average' => $average);
}
print_r(variance($arr1));
print_r(variance($arr2));

The above code prints

Array
(
  [variance] => 536
  [square] => 23.15167380558
  [average] => 72
)
Array
(
  [variance] => 3.6
  [square] => 1.897366596101
  [average] => 72
)

It is found by looking at the data that although the average of the two arrays is the same , but array 1 has large fluctuations and the results are unstable, while array 2 has small fluctuations and the results are more stable than array 1.

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