A teacher asks her students to write down the number of hours studied, rounded to the nearest half hour. She compiles the results and develops the probability distribution below for a randomly selected student.

What is the mean of the probability distribution?

\begin{tabular}{|c|c|}
\hline \multicolumn{2}{|c|}{ Probability Distribution } \\
\hline \begin{tabular}{c}
Hours \\
Studied: [tex]$x$[/tex]
\end{tabular} & Probability: [tex]$P(X)$[/tex] \\
\hline 0.5 & 0.07 \\
\hline 1 & 0.2 \\
\hline 1.5 & 0.46 \\
\hline 2 & 0.2 \\
\hline 2.5 & 0.07 \\
\hline
\end{tabular}



Answer :

To find the mean of the given probability distribution, we need to use the formula for the expected value (mean) of a discrete random variable. The expected value [tex]\(E(X)\)[/tex] is given by:

[tex]\[ E(X) = \sum_{i=1}^{n} x_i \cdot P(X = x_i) \][/tex]

Where [tex]\(x_i\)[/tex] represents each value of the random variable (in this case, the number of hours studied) and [tex]\(P(X = x_i)\)[/tex] is the corresponding probability.

We have the following data from the distribution table:
[tex]\[ \begin{array}{|c|c|} \hline \text{Hours Studied} (x_i) & \text{Probability} (P(X = x_i)) \\ \hline 0.5 & 0.07 \\ \hline 1.0 & 0.20 \\ \hline 1.5 & 0.46 \\ \hline 2.0 & 0.20 \\ \hline 2.5 & 0.07 \\ \hline \end{array} \][/tex]

Next, we compute the product of each value [tex]\(x_i\)[/tex] with its corresponding probability [tex]\(P(X = x_i)\)[/tex]:

1. For [tex]\(x = 0.5\)[/tex]:
[tex]\[ 0.5 \times 0.07 = 0.035 \][/tex]

2. For [tex]\(x = 1.0\)[/tex]:
[tex]\[ 1.0 \times 0.20 = 0.20 \][/tex]

3. For [tex]\(x = 1.5\)[/tex]:
[tex]\[ 1.5 \times 0.46 = 0.69 \][/tex]

4. For [tex]\(x = 2.0\)[/tex]:
[tex]\[ 2.0 \times 0.20 = 0.40 \][/tex]

5. For [tex]\(x = 2.5\)[/tex]:
[tex]\[ 2.5 \times 0.07 = 0.175 \][/tex]

Finally, we sum these products to find the expected value (mean):

[tex]\[ E(X) = 0.035 + 0.20 + 0.69 + 0.40 + 0.175 \][/tex]

[tex]\[ E(X) = 1.5 \][/tex]

So, the mean number of hours studied for this probability distribution is [tex]\(1.5\)[/tex] hours.