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4.1.1 Probability (A-level only)

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Question 68

A botanical research station analyzes 50 plant samples for the presence of three specific enzymes: Alpha (AAA), Beta (BBB), and Gamma (ΓΓΓ). The distribution of these enzymes across the samples is summarized in the following data:

\begin{itemize} \item 9 samples contain only enzyme A.\item6samplescontainbothenzymes. \item 6 samples contain both enzymes .\item6samplescontainbothenzymesA,andandandB,butnot, but not ,butnotΓ.\item11samplescontainonlyenzyme. \item 11 samples contain only enzyme .\item11samplescontainonlyenzymeB.\item4samplescontainbothenzymes. \item 4 samples contain both enzymes .\item4samplescontainbothenzymesB,andandandΓ,butnot, but not ,butnotA.\item8samplescontainonlyenzyme. \item 8 samples contain only enzyme .\item8samplescontainonlyenzymeΓ.\item12samplescontainnoneoftheseenzymes.\itemNosamplescontainboth. \item 12 samples contain none of these enzymes. \item No samples contain both .\item12samplescontainnoneoftheseenzymes.\itemNosamplescontainbothA,andandandΓ, simultaneously. \end{itemize}

One sample is selected at random.

a.

Show that the probability that the sample contains more than one enzyme is 0.2.

[2]
b.

Determine the probability that the sample contains enzyme A A\,A or enzyme BBB (or both).

[2]
c.

State the probability that the sample contains both enzyme A A\,A and enzyme ΓΓΓ.

[1]
d.

Given that the sample is found to contain at least one of the three enzymes,

calculate the probability that it contains enzyme ΓΓΓ.

[3]
e.

Determine, with a reason, whether the presence of enzyme B B\,B and the presence of enzyme Γ Γ\,Γ in a sample are statistically independent events.

[4]

4.1.1 Probability (A-level only) Questions

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