In​ long-run equilibrium, all firms in the industry earn zero economic profit. Why is this​ true? All firms in perfectly competitive industries earn zero economic profit in the long run because A. barriers to entry and exit prevent firms from earning positive or negative economic profit. B. a positive profit would induce firms to produce more ​, increasing price and​ profit, and a negative profit would induce firms to produce less ​, decreasing price and profit. C. firms are price​ takers, maximizing profit by producing where price equals average cost . D. a positive profit would induce firms to​ enter, decreasing price and​ profit, and a negative profit would induce firms to​ exit, increasing price and profit. E. firms are price​ takers, maximizing profit by producing where price equals marginal cost.

Cosmetic profits. sally is the executive vice president of big name cosmetics company. through important and material, nonpublic information, she learns that the company is soon going to purchase a smaller chain of stores. it is expected that stock in big name cosmetics will rise dramatically at that point. sally immediately buys a number of shares of her company's stock. she also tells her friend alice about the expected purchase of stores. alice wanted to purchase stock in the company but lacked the funds with which to do so. although she did not have the funds in bank a, alice decided to draw a check on bank a and deposit the check in bank b and then proceed to write a check on bank b to cover the purchase of the stock. she hoped that she would have sufficient funds to deposit before the check was presented for payment. of which of the following offenses, if any, is alice guilty of by buying stock?

Reliability and validity reliability and validity are two important considerations that must be made with any type of data collection. reliability refers to the ability to consistently produce a given result. in the context of psychological research, this would mean that any instruments or tools used to collect data do so in consistent, reproducible ways. unfortunately, being consistent in measurement does not necessarily mean that you have measured something correctly. to illustrate this concept, consider a kitchen scale that would be used to measure the weight of cereal that you eat in the morning. if the scale is not properly calibrated, it may consistently under- or overestimate the amount of cereal that’s being measured. while the scale is highly reliable in producing consistent results (e. g., the same amount of cereal poured onto the scale produces the same reading each time), those results are incorrect. this is where validity comes into play. validity refers to the extent to which a given instrument or tool accurately measures what it’s supposed to measure. while any valid measure is by necessity reliable, the reverse is not necessarily true. researchers strive to use instruments that are both highly reliable and valid.

The textbook defines ethics as “the principles of conduct governing an individual or a group,” and specifically as the standards one uses to decide what their conduct should be. to what extent do you believe that what happened at bp (british petrolium) is as much a breakdown in the company’s ethical systems as it is in its safety systems, and how would you defend your conclusion?