The correct answer is <span>the values are measures for the sampling distribution of the mean
For example, in the </span>μm it is used to<span> represent the mean of the distribution of sample </span>means, while in the σm it is indicated that this value is a standard deviation, and just the M means that it is the standard deviation for the distribution of sample <span>means</span>
There were lots of foreign changes that presented challenges for the US. I'll give you a few examples from different time periods. First would be when England wanted to tax the Americans in the Revolutionary period. They did this to try and restrict America's freedom. Another example would be that Russia had spies during the cold war period. This was to gain intelligence of the US war plans. Also when Germany sent the Zimmerman Telegram to Mexico during the WWII period. This was to get Mexico to launch a surprise attack on the US.
One of the main ways in which travel routes today differ from the trade routes of classical era civilizations is that they're far safer, since people have to worry much less about being robbed and/or injured--this is due mostly to government oversight and policing of the routes in question.<span />
