Question 1

Paper 1, no calculatorEasy5 marks

A clinic records whether each of 100 patients has a particular exposure, EE and whether they have a condition, DD Figure 1 shows the results.

50454035302520151050Number of patientsCondition (D)No condition (D′)Exposed (E)Not exposed (E′)Exposure status
(a)

Write down the formula for P(D∣E)P(D\mid E) assuming P(E)>0P(E)>0

[1]
(b)

Use Figure 1 for both parts.

(i)

Calculate P(D∣E)P(D\mid E)

[2]
(ii)

Determine whether DD and EE are independent. Give a reason.

[2]

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