:4. Solution. The first statement is true since the population histogram follows the normal curve.
The second statement is false since the SE of the population incomes is $5,000, not $500.
: the chance that X is between $19,000 and $21,000 is either 0% or 100%.
The fourth statement is true since the SE of the sample average is $5.000/10 = $500.
The correct answer is "two".