Which of the given facts regarding Alexa are accurate: (i) Alexa give free data on the relative website visitor traffic. (ii) Alexa and Quant cast offer information on visitor household incomes. (iii) Alexa is biased in the direction of US based traffic. (iv) Quant cast merely tracks the people who have installed Quant cast toolbar.
Can someone please help me in finding out the accurate answer from the above options?