问一道题：NO.PZ2017092702000148

问题如下：

Which of the following groups best illustrates a population?

选项：

The 500 companies in the S&P 500 Index

The NYSE-listed stocks in the Dow Jones Industrial Average

The Lehman Aggregate Bond Index as a representation of the US bond market

解释：

A is correct. A population is defined as all members of a specified group. The S&P 500 Index consists of 500 companies, so this group is the population of companies in the index.
B is incorrect because there are several Dow Jones component stocks that are not traded on the NYSE, making the NYSE group a subset of the total population of stocks included in the Dow Jones average.
C is incorrect because although the Lehman Aggregate Bond Index is representative of the US bond market, it is a sampling of bonds in that market and not the entire population of bonds in that market.