The histogram shows the distribution of household sizes in the United States for a recent year.

1. Find the mean of the probability distribution to three significant digits.
   {#1}
   
   
2. Find the variance of the probability distribution to three significant digits.
   {#2}
   
   
3. Find the standard deviation of the probability distribution to three significant digits.
   {#3}
   
   
4. Find the expected value of the probability distribution to three significant digits.
   {#4}