Security X has expected return of 12% and standard deviation of 20%. Security Y has expected return of 15% and standard deviation of 27%. If the two securities have a correlation coefficient of 0.7, what is their covariance?

An airline initially has a single price of $200 for all consumers. At this price, it sells 400 business tickets and 700 tourist tickets. The airline's marginal cost is $50. The slope of the business demand curve is 2.0 (in absolute value), and the slope of the tourist demand curve is 0.1 (in absolute value). How can the airline increase its profits, assuming that it can separate the market and prevent resale?

It is not uncommon:

Which of the following is false concerning foreign currency bid-ask spreads?

A statistician is calculating the confidence interval for but the standard deviation of the sampled population is unknown. It is acceptable to use the sample standard deviation in place of the population standard deviation when
I). when the sample distribution is normally distributed.
II). the sample size is greater than 30.
III). when the sample distribution behaves according to the Central Limit Theorem.