Question

Josh counted the number of problems on each of his tests. Number of problems Number of tests 9 3 34 2 6 39 41 3 2 50 4. 95 X is the number of problems that a randomly chosen test had. What is the expected value of X? Write your answer as a decimal.

Answer 1

The expecting value E(x) is given by

$E(x)=\frac{\Sigma x_j\cdot t_j}{n}$

where x is the number of problems and t the number of test and n is the total of tests.

By substituting our values, we get

$E(x)=\frac{9\cdot3+34\cdot2+39\cdot6+41\cdot3+50\cdot2+95\cdot4}{3+2+6+3+2+4}$

which gives

$\begin{gathered} E(x)=\frac{932}{20} \\ E(x)=46.6 \end{gathered}$

that is, the expected values is 46.6