Questions: Conditional probability: Basic
It is estimated that 89% of senior citizens suffer from sleep disorders and 9% suffer from anxiety. Moreover, 5% of senior citizens suffer from both sleep disorders and anxiety.
Answer the questions below. (If necessary, consult a list of formulas.)
(a) Find the probability that a senior citizen suffers from anxiety, given that he or she has sleep disorder. Round your answer to 2 decimal places.
(b) Given that a senior citizen suffers from anxiety, what is the probability that he or she also suffers from sleep disorder? Round your answer to 2 decimal places.
Transcript text: Conditional probability: Basic
It is estimated that $89 \%$ of senior citizens suffer from sleep disorders and $9 \%$ suffer from anxiety. Moreover, $5 \%$ of senior citizens suffer from both sleep disorders and anxiety.
Answer the questions below. (If necessary, consult a list of formulas.)
(a) Find the probability that a senior citizen suffers from anxiety, given that he or she has sleep disorder. Round your answer to 2 decimal places.
$\square$
(b) Given that a senior citizen suffers from anxiety, what is the probability that he or she also suffers from sleep disorder? Round your answer to 2 decimal places.
$\square$
Solution
Solution Steps
Step 1: Identify the given probabilities
Probability of sleep disorder (\( P(A) \)) = \( 89\% = 0.89 \).
Probability of anxiety (\( P(B) \)) = \( 9\% = 0.09 \).
Probability of both sleep disorder and anxiety (\( P(A \cap B) \)) = \( 5\% = 0.05 \).
Step 2: Solve part (a) - Find \( P(B \mid A) \)
The conditional probability formula is:
\[
P(B \mid A) = \frac{P(A \cap B)}{P(A)}
\]
Substitute the given values:
\[
P(B \mid A) = \frac{0.05}{0.89} \approx 0.0562
\]
Round to 2 decimal places:
\[
P(B \mid A) \approx 0.06
\]
Step 3: Solve part (b) - Find \( P(A \mid B) \)
The conditional probability formula is:
\[
P(A \mid B) = \frac{P(A \cap B)}{P(B)}
\]
Substitute the given values:
\[
P(A \mid B) = \frac{0.05}{0.09} \approx 0.5556
\]
Round to 2 decimal places:
\[
P(A \mid B) \approx 0.56
\]