如何計算標準差?

我想寫近五年的最高價PE，平均PE的標準差，但跑出來為0，請教要怎麼寫? 謝謝

Year_EPS0=GetField("EPS","Y");

Year_EPS1=GetField("EPS","Y")[1];

Year_EPS2=GetField("EPS","Y")[2];

Year_EPS3=GetField("EPS","Y")[3];

Year_EPS4=GetField("EPS","Y")[4];

Year_Highest_Price1=HighY(1); 

Year_Highest_Price2=HighY(2);

Year_Highest_Price3=HighY(3);

Year_Highest_Price4=HighY(4);

Year_Highest_Price5=HighY(5);

Year_PE_High1=round(Year_Highest_Price1/Year_EPS0,2);

Year_PE_High2=round(Year_Highest_Price2/Year_EPS1,2);

Year_PE_High3=round(Year_Highest_Price3/Year_EPS2,2);

Year_PE_High4=round(Year_Highest_Price4/Year_EPS3,2);

Year_PE_High5=round(Year_Highest_Price5/Year_EPS4,2);

value1=(Year_PE_High1+Year_PE_High2+Year_PE_High3+Year_PE_High4+Year_PE_High5)/5;

value2=StandardDev(value1,1,1);