C# ST DEV. Please Help ASAP

Guys. Im a c# noob but I really need a professional's help. I am using visual studio 2005 for a project so I dont have math.linq I need to calculate the standard deviation of a generic list of objects. The list contains just a list of float numbers, nothing too complicated. However I have never done this before so i need someone to show me that has calculated standard deviation of a generic list before. Here is my code that I tried to start on:

//this is my list of objects inside. The valve data just contains a bunch of floats.
public class ValveDataResults
{
private List<ValveData> m_ValveResults;

public void AddValveData(ValveData valve)
{
m_ValveResults.Add(valve);
}
//this is the function where the standard deviation needs to be calculated:
public float LatchTimeStdev()
{
//below this is a working example of how to get an average or mean
//of same list and same "LatchTime" that needs to be calculated here as well.
}
//function to calculate average of latch time, can be copied for above st dev.
public float LatchTimeMean()
{
float returnValue = 0;
foreach (ValveData value in m_ValveResults)
{
returnValue += value.LatchTime;
}
returnValue = (returnValue / m_ValveResults.Count) * 0.02f;
return returnValue;
}

the "Latch Time" is a float object of the "ValveData" object which is inserted into the m_ValveResults list.

thats it. any help would much be appreciated. Thanks

All you need is to calculate the standard deviation?

I feel like I am missing something but here you go

Code:

---

        public static float LatchTimeStdev()
        {
            float sum = 0.0f ;
            float mean = LatchTimeMean();
            for (int i = 0; i < m_ValveResults.Count; i++)
            {
                float val = (mean - m_ValveResults[i].LatchTime);
                sum += val * val;
            }
            return (float)Math.Sqrt(sum / (m_ValveResults.Count - 1));
        }

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