Write the null and alternative hypotheses to test each of the following situations.
a) An online clothing company is concerned about the timeliness of their deliveries. The VP of Operations and Marketing recently stated that she wanted the percentage of products delivered on time to be greater than 90%, and she wants to know if the company has succeeded.
b) A realty company recently announced that the proportion of houses taking more than three months to sell is now greater than 50%.
c) A financial firm’s accounting department reports that after improvements in their system, they now have an error rate below 2 %.