Question
6 There is a 25% chance that Claire will have to work tonight and cannot study for the big math test. If Claire studies, then she has an 80% chance of earning a good grade. If she does not study, she only has a 30% chance of earning a good grade. a. Draw a diagram to represent this situation. b. Calculate the probability of Claire earning a good grade on the math test. c.If Claire earned a good grade, what is the probability that she studied?
Answer
4.1
(310 Votes)
Iola
Elite · Tutor for 8 years
Answer
### Probability of Claire earning a good grade is
.### Probability that Claire studied given she earned a good grade is
.# Calculation Details:### Diagram:
### Calculate Overall Probability of Good Grade:1. Probability Claire works and earns a good grade: \( P(\text{Good Grade} | \text{Work}) = 0.25 \times 0.30 = 0.075 \)2. Probability Claire does not work and earns a good grade: \( P(\text{Good Grade} | \text{No Work}) = 0.75 \times 0.80 = 0.60 \)3. Total Probability \( P(\text{Good Grade}) \):
### Calculate Conditional Probability (Bayes' Theorem):
1. \( P(\text{Good Grade} | \text{Studied}) = 0.80 \)2. \( P(\text{Studied}) = 0.75 \)3. Therefore,
Explanation
## Step 1: Draw a Diagram### Draw a probability tree that represents all events: Claire working or not working, and Claire earning a good grade or not earning a good grade.## Step 2: Calculate Overall Probability of Good Grade### Calculate the total probability Claire earns a good grade using the Law of Total Probability. ## Step 3: Calculate Conditional Probability### Apply Bayes' Theorem to find the probability that Claire studied given that she earned a good grade.