def round_to(x)
  (self * 10**x).round.to_f / 10**x
end

def std(bia, decs, nums)
  sum = 0.0
  count = 0.0
  nums.each { |plus| sum += plus
    count += 1 }

  puts "The sum of numbers in the array is: #{sum}"
  puts "The total numbers in your array is: #{count}"
  mean = sum / count
  dec_round = "#{decs}"
  rounded_mean = mean.round_to(dec_round)
  puts rounded_mean
puts "The mean of all the numbers in your array is: #{mean}"

    if bia == "biased"
    bia_nums = 0.0
    nums.each { |a| bia_nums += ((mean - a)**2) }
    stddev_biased = Math.sqrt(bia_nums / (count - 1))
  puts "The biased standard deviation is: #{stddev_biased}"

    elsif bia == "unbiased"
    unbia_nums = 0.0
    nums.each { |a| unbia_nums += ((mean - a)**2) }
    stddev_unbiased = Math.sqrt(unbia_nums / (count))
  puts "The unbiased standard deviation is: #{stddev_unbiased}"

    else
  print 'That is not the right syntax, use std("biased", [1,2,3])'
    end
end