Some people have argued that the market portfolio can never be measured and that the CAPM, therefore,

Question:

Some people have argued that the market can never be measured and that the CAPM, therefore, is untestable. Others have argued that APT specifies neither the number of factors nor their identity and, hence, is also untestable. If these views are correct, are the theories valueless? Explain.
Portfolio
A portfolio is a grouping of financial assets such as stocks, bonds, commodities, currencies and cash equivalents, as well as their fund counterparts, including mutual, exchange-traded and closed funds. A portfolio can also consist of non-publicly...