A movie company surveyed 1000 people. 229 people said they went to see the new movie on Friday, 256 said they went on Saturday. If 24 people say the movie both nights, what is the probability that person chosen at random saw the movie on Friday or Saturday?

Responses

0.437

1 answer

To find the probability that a randomly chosen person saw the movie on either Friday or Saturday, we can use the principle of inclusion-exclusion.

Let:

  • \( A \) be the event that a person saw the movie on Friday.
  • \( B \) be the event that a person saw the movie on Saturday.

From the data provided:

  • \( |A| = 229 \) (number of people who went on Friday)
  • \( |B| = 256 \) (number of people who went on Saturday)
  • \( |A \cap B| = 24 \) (number of people who went both nights)

We want to find \( |A \cup B| \), the number of people who saw the movie on at least one of the two nights, which is given by the formula:

\[ |A \cup B| = |A| + |B| - |A \cap B| \]

Substituting in the values:

\[ |A \cup B| = 229 + 256 - 24 \] \[ |A \cup B| = 461 \]

Now, to find the probability \( P(A \cup B) \) that a randomly chosen person saw the movie on either night, we divide the number of people who saw the movie by the total number of people surveyed:

\[ P(A \cup B) = \frac{|A \cup B|}{\text{Total number of people}} = \frac{461}{1000} \]

Thus, the probability is:

\[ P(A \cup B) = 0.461 \]

Therefore, the probability that a person chosen at random saw the movie on Friday or Saturday is 0.461.

(Note: The response "0.437" is incorrect based on the calculations above.)