So what I've been given: Mean.cc is a class that inherits polymorphically from Statistic.h (the only things defined in that class are virtual void Collect(double) = 0; and virtual double Calculate() const = 0;)

So the mean.cc is defined as:

/* Stores data (datum) such than an average may be calculated.
 * - NOTE: You do not necessarily need to store each datum.
 */
     void Collect(double datum);

/* Returns the mean of the data (datum) from the Collect method.
 */
     double Calculate() const;

And the methods need to be able to pass these tests:

  void TestMeanCollect(Statistic* stat) 
  {
    const double kData[] = {34, 54, 99, 102, 43};
    const unsigned int kSize = sizeof(kData) / sizeof(double);

    for (unsigned int i = 0; i < kSize; ++i)
    stat->Collect(kData[i]);
   }`

   bool TestMeanCalculate(Statistic* stat) 
  {
    const double kData[] = {34, 54, 99, 102, 43};
    const unsigned int kSize = sizeof(kData) / sizeof(double);
    const double kExpected = (34 + 54 + 99 + 102 + 43) / 5.0;

    for (unsigned int i = 0; i < kSize; ++i)
    stat->Collect(kData[i]);

    double actual = stat->Calculate();
    if (kExpected != actual) {
    cout << "  Expected: " << kExpected << ", Actual: " << actual << 
    endl;
    return false;
   }

  return true;
}

What I'm confused about is, can someone please explain the logic of how to do either of these methods? I'm not requesting straight code, I just need an idea of where to start because I'm drawing a complete blank. The way I tried it before is as shown below, but I've been told that that ignores the functions parameters/negates what the actual method is being asked to do.

void Collect(double datum)
  {
      double datum = 0;
      int kSize = 5;
      double kData[5];
      cout << "You can enter 5 values" << endl;
      cout << "Please enter your values" << endl;
      for (int i = 0; i < kSize; ++i)
      {
          cin >> kData[i];
          datum += kData[i];
      }
      datum = datum / kSize;
  }