Function to find standard deviation of grouped data .
function groupedSD ( lower_limit , upper_limit , freq , n ) { let mid = [ ] ; let sum = 0 , freqSum = 0 , sd ; for ( let i = 0 ; i < n ; i ++ ) { mid [ i ] = ( lower_limit [ i ] + upper_limit [ i ] ) / 2 ; sum = sum + freq [ i ] * mid [ i ] * mid [ i ] ; freqSum = freqSum + freq [ i ] ; }