Photo AI

Given that $$P(A) = 0.35 \quad P(B) = 0.45 \quad \text{and} \quad P(A \cap B) = 0.13$$ find (a) \( P(A' | B') \) (2) (b) Explain why the events A and B are not independent - Edexcel - A-Level Maths Statistics - Question 4 - 2017 - Paper 2

Question icon

Question 4

Given-that--$$P(A)-=-0.35-\quad-P(B)-=-0.45-\quad-\text{and}-\quad-P(A-\cap-B)-=-0.13$$--find--(a)-\(-P(A'-|-B')-\)-(2)--(b)-Explain-why-the-events-A-and-B-are-not-independent-Edexcel-A-Level Maths Statistics-Question 4-2017-Paper 2.png

Given that $$P(A) = 0.35 \quad P(B) = 0.45 \quad \text{and} \quad P(A \cap B) = 0.13$$ find (a) \( P(A' | B') \) (2) (b) Explain why the events A and B are not i... show full transcript

Worked Solution & Example Answer:Given that $$P(A) = 0.35 \quad P(B) = 0.45 \quad \text{and} \quad P(A \cap B) = 0.13$$ find (a) \( P(A' | B') \) (2) (b) Explain why the events A and B are not independent - Edexcel - A-Level Maths Statistics - Question 4 - 2017 - Paper 2

Step 1

Find \( P(A' | B') \)

96%

114 rated

Answer

To find ( P(A' | B') ), we can use the formula:

P(AB)=1P(AB)P(A' | B') = 1 - P(A | B)

First, we find ( P(A | B) ) using:

P(AB)=P(AB)P(B)=0.130.450.2889P(A | B) = \frac{P(A \cap B)}{P(B)} = \frac{0.13}{0.45} \approx 0.2889

Now, substituting into our original formula:

P(AB)=10.28890.7111P(A' | B') = 1 - 0.2889 \approx 0.7111

Step 2

Explain why the events A and B are not independent.

99%

104 rated

Answer

Events A and B are not independent because:

P(AB)P(A)P(B)P(A \cap B) \neq P(A) \cdot P(B)

Calculating, we find:

P(AB)=0.13andP(A)P(B)=0.350.45=0.1575P(A \cap B) = 0.13 \quad \text{and} \quad P(A) \cdot P(B) = 0.35 \cdot 0.45 = 0.1575

Since ( 0.13 \neq 0.1575 ), the events are dependent.

Step 3

Draw a Venn diagram to illustrate the events A, B and C.

96%

101 rated

Answer

In the Venn diagram:

  • Region for A only contains 0.22
  • Region for B only contains 0.09
  • Region for C only has 0.20
  • The overlap between A and B contains 0.13
  • The area A and C overlaps shows 0.00 since they are mutually exclusive.

Each region should be clearly labeled to show these probabilities.

Step 4

Find \( P(B \cup C') \)

98%

120 rated

Answer

Using the formula for the union of two probabilities:

P(BC)=P(B)+P(C)P(BC)P(B \cup C') = P(B) + P(C') - P(B \cap C')

We know:

  • ( P(B) = 0.45 )
  • ( P(C') = 1 - P(C) = 1 - 0.20 = 0.80 )
  • To find ( P(B \cap C') ), we use the independence state of B and C:

Thus:

P(BC)=P(B)P(C)=0.450.80=0.36P(B \cap C') = P(B) \cdot P(C') = 0.45 \cdot 0.80 = 0.36

Calculating:

P(BC)=0.45+0.800.36=0.89P(B \cup C') = 0.45 + 0.80 - 0.36 = 0.89

Join the A-Level students using SimpleStudy...

97% of Students

Report Improved Results

98% of Students

Recommend to friends

100,000+

Students Supported

1 Million+

Questions answered

;