Question 947830
A sample space is a set of all possible outcomes for an activity or experiment.

four births, boy or girl will have {{{4*4=16}}} possible outcomes
 
Let's build the tree to:


<img src="http://i150.photobucket.com/albums/s91/jim_thompson5910/work/w5a39a-2.png">


Using the tree, we get the sample space:


{b,b,b,b}
{b,b,b,g}
{b,b,g,b}
{b,b,g,g}
{b,g,b,b}
{b,g,b,g}
{b,g,g,b}
{b,g,g,g}


{g,b,b,b}
{g,b,b,g}
{g,b,g,b}
{g,b,g,g}
{g,g,b,b}
{g,g,b,g}
{g,g,g,b}
{g,g,g,g}

so, there is {{{16}}} possible outcomes all together 

So for instance {b,g,g,b} means that the couple had a boy, girl, girl, and then a boy (in that order).


Note: recall, the sample space is the set of ALL possible outcomes.