document.write( "Question 896413: A researcher calculated the values and probabilities for a random variable X as shown below. Unfortunately, he erased the last value and needs to figure out what it was. If the mean of X was 2.2, then what was the last value?
\n" ); document.write( "X
\n" ); document.write( "0
\n" ); document.write( "1
\n" ); document.write( "3
\n" ); document.write( "?
\n" ); document.write( "P(X)
\n" ); document.write( "0.4
\n" ); document.write( "0.1
\n" ); document.write( "0.2
\n" ); document.write( "0.3
\n" ); document.write( " \n" ); document.write( "
Algebra.Com's Answer #543492 by stanbon(75887)\"\" \"About 
You can put this solution on YOUR website!
A researcher calculated the values and probabilities for a random variable X as shown below. Unfortunately, he erased the last value and needs to figure out what it was. If the mean of X was 2.2, then what was the last value?
\n" ); document.write( "X
\n" ); document.write( "0
\n" ); document.write( "1
\n" ); document.write( "3
\n" ); document.write( "?
\n" ); document.write( "P(X)
\n" ); document.write( "0.4
\n" ); document.write( "0.1
\n" ); document.write( "0.2
\n" ); document.write( "0.3
\n" ); document.write( "------
\n" ); document.write( "Sounds like a weighted-mean problem.
\n" ); document.write( "Equation:
\n" ); document.write( "0.4*0 + 0.1*1 + 0.2*3 + 0.3*X = 2.2
\n" ); document.write( "------
\n" ); document.write( "0 + 0.1 + 0.6 + 0.3X = 2.2
\n" ); document.write( "0.7 + 0.3X = 2.2
\n" ); document.write( "0.3x = 1.5
\n" ); document.write( "X = 5
\n" ); document.write( "----------------------
\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H. \n" ); document.write( "
\n" );