title: If/ Elses statement not executing properly
body: <p>I've altered the if/else statements several times and either <strong>only</strong> the if statement will be executed even if it's not true or <strong>only</strong> the else statement will be executed even if it's not true.</p>
  
  <pre><code>def interview():
  """ NoneType -&gt; NoneType
  Interview the user. """
  name = input("What is your name?")
  unit = input("What is you preferred choice of unit - standard or imperial?")
  weight = float(input("What is your weight?"))
  height = float(input("What is your height?"))
  a = float(bmi_std(weight, height))
  b = float(bmi_std_prime(weight, height))
  c = float(bmi_imp(weight, height))
  d = float(bmi_imp_prime(weight, height))
  e = str(category(weight, height, 's'))
  f = str(category(weight, height, 'i'))
  
  print("So," + name + ", your preferred unit is" + unit + ".")
  print("Your weight", weight)
  print("Your height", height)
  if str(unit == 'imperial'):
      print("BMI = " + str(c) + " and your BMI prime = " + str(d))
      print("Category = " + f)
  else:
      print("BMI = " + str(a) + " and your BMI prime = " + str(b))
      print("Category = " + e)
  </code></pre>
  
  <p>This is just part of my code. Is there something wrong in the way its written because it looks fine to me. I'm only an intro to programming.</p>