Chapter 07 – Capital Asset Pricing and Arbitrage Pricing Theory
a. Shorting equal amounts of the 10 negative-alpha stocks and investing the proceeds
= $1,000,000 0.06 = $60,000
The sensitivity of the payoff of this portfolio to the market factor is zero because the
exposures of the positive alpha and negative alpha stocks cancel out. (Notice that
the terms involving RM sum to zero.) Thus, the systematic component of total risk
also is zero. The variance of the analyst’s profit is not zero, however, since this
20 [(100,000 0.30)2] = 18,000,000,000
The standard deviation of dollar returns is $134,164.
b. If n = 50 stocks (i.e., 25 long and 25 short), $40,000 is placed in each position,
and the variance of dollar returns is:
50 [(40,000 0.30)2] = 7,200,000,000
Notice that when the number of stocks increases by a factor of 5 (from 20 to 100),
standard deviation falls by a factor of
= 2.236, from $134,164 to $60,000.
30. Any pattern of returns can be “explained” if we are free to choose an indefinitely large
31. The APT factors must correlate with major sources of uncertainty, i.e., sources of
uncertainty that are of concern to many investors. Researchers should investigate
factors that correlate with uncertainty in consumption and investment opportunities.