2012 A-level H2 Mathematics (9740) Paper 2 Question 5 Suggested Solutions

By KS Teng

All solutions here are SUGGESTED. Mr. Teng will hold no liability for any errors. Comments are entirely personal opinions.

(i)
(a)
\mathrm{P} (test ~postiive)

= 0.001 \times 0.995 + 0.999 \times 0.005

= 0.00599

(b)
\mathrm{P} (disease~ | ~test positive)

\frac{\mathrm{P} (disease ~\cap~ test positive)}{\mathrm{P}(test ~positive)}

\frac{0.001 \times 0.995}{0.00599}

\approx 0.166

(ii)
\mathrm{P}(disease~ |~ test positive ) = 0. 75

\frac{\mathrm{P} (disease ~\cap~ test positive)}{\mathrm{P}(test~ positive)} = 0.75

\frac{0.001p}{0.001p + 0.999(1-p)} = 0.75

Using the Graphing Calculator, p \approx 0.999666

KS Comments:

Students will find it helpful to start this question with a tree diagram.

Comments
    pingbacks / trackbacks

    Leave a Comment

    Contact Us

    CONTACT US We would love to hear from you. Contact us, or simply hit our personal page for more contact information

    Not readable? Change text. captcha txt
    0

    Start typing and press Enter to search

    2012 A-level H2 Mathematics (9740) Paper 2 Question 4 Suggested SolutionsJC Mathematics
    2012 A-level H2 Mathematics (9740) Paper 2 Question 6 Suggested SolutionsJC Mathematics