2.40.∗ Aninterval scale for which ratios are valid is called a ratio scale. Such scales have a well-defined 0 point, so, for instance, one can regard the value 20 as twice the quantity of the value 10. Explain why annual income is measured on a ratio scale, but temperature (in Fahrenheit or Centigrade)

is not. Is IQ, as a measure of intelligence, a ratioscale variable? Explain.