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A gymnastics coach records the scores of a gymnast and develops the probability distribution below. What is the probability the gymnast scores a 9 or 9.5?

\begin{tabular}{|c|c|}
\hline \multicolumn{2}{|c|}{ Probability Distribution } \\
\hline \begin{tabular}{c}
Gymnastics \\
Score: [tex]$X$[/tex]
\end{tabular} & Probability: [tex]$P(X)$[/tex] \\
\hline 5 & 0.02 \\
\hline 5.5 & 0.02 \\
\hline 6 & 0.06 \\
\hline 6.5 & 0.1 \\
\hline 7 & 0.16 \\
\hline 7.5 & 0.14 \\
\hline 8 & 0.18 \\
\hline 8.5 & 0.18 \\
\hline 9 & [tex]$?$[/tex] \\
\hline 9.5 & 0.02 \\
\hline
\end{tabular}


Sagot :

First, let's extract the relevant information from the given probability distribution table. We know the following probabilities:

- The probability that the gymnast scores a 5 is [tex]\( P(X = 5) = 0.02 \)[/tex]
- The probability that the gymnast scores a 5.5 is [tex]\( P(X = 5.5) = 0.02 \)[/tex]
- The probability that the gymnast scores a 6 is [tex]\( P(X = 6) = 0.06 \)[/tex]
- The probability that the gymnast scores a 6.5 is [tex]\( P(X = 6.5) = 0.1 \)[/tex]
- The probability that the gymnast scores a 7 is [tex]\( P(X = 7) = 0.16 \)[/tex]
- The probability that the gymnast scores a 7.5 is [tex]\( P(X = 7.5) = 0.14 \)[/tex]
- The probability that the gymnast scores an 8 is [tex]\( P(X = 8) = 0.18 \)[/tex]
- The probability that the gymnast scores an 8.5 is [tex]\( P(X = 8.5) = 0.18 \)[/tex]
- The probability that the gymnast scores a 9 is [tex]\( P(X = 9) = 0 \)[/tex]
- The probability that the gymnast scores a 9.5 is [tex]\( P(X = 9.5) = 0.02 \)[/tex]

The objective is to find the probability that the gymnast scores either a 9 or a 9.5. To do this, we can simply add together the individual probabilities for these two specific scores:

[tex]\[ P(X = 9 \text{ or } X = 9.5) = P(X = 9) + P(X = 9.5) \][/tex]

From the information provided:
[tex]\[ P(X = 9) = 0 \][/tex]
[tex]\[ P(X = 9.5) = 0.02 \][/tex]

Adding these probabilities together, we get:
[tex]\[ P(X = 9 \text{ or } X = 9.5) = 0 + 0.02 = 0.02 \][/tex]

Thus, the probability that the gymnast scores a 9 or a 9.5 is:
[tex]\[ \boxed{0.02} \][/tex]