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Date November 2018 Marks available 2 Reference code 18N.1.SL.TZ0.T_14
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Find Question number T_14 Adapted from N/A

Question

The marks achieved by students taking a college entrance test follow a normal distribution with mean 300 and standard deviation 100.

In this test, 10 % of the students achieved a mark greater than k.

Marron College accepts only those students who achieve a mark of at least 450 on the test.

Find the value of k.

[2]
a.

Find the probability that a randomly chosen student will be accepted by Marron College.

[2]
b.

Given that Naomi attends Marron College, find the probability that she achieved a mark of at least 500 on the test.

[2]
c.

Markscheme

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

    (M1)

Note: Award (M1) for diagram that shows the correct shaded area and percentage, k has to be greater than the mean.

OR

Award (M1) for P(mark > k) = 0.1 or P(mark ≤ k) = 0.9 seen.

 

428  (428.155…)      (A1) (C2)

 

[2 marks]

a.

  (M1)

Note: Award (M1) for diagram that shows the correct shaded area and the value 450 labelled to the right of the mean.

OR

Award (M1) for P(mark ≥ 450) seen.

 

0.0668  (0.0668072…, 6.68 %, 6.68072… %)      (A1) (C2)

 

[2 marks]

b.

0.0228 0.0668     ( 0.0227500 0.0668072 )         (M1)

Note: Award (M1) for 0.0228 (0.0227500…) seen. Accept 1 − 0.97725.

 

= 0.341   (0.340532…, 34.1 %, 34.0532…%)      (A1)(ft) (C2)

Note: Follow through from part (b), provided answer is between zero and 1.

 

[2 marks]

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Topic 4—Statistics and probability » SL 4.6—Combined, mutually exclusive, conditional, independence, prob diagrams
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Topic 4—Statistics and probability » SL 4.9—Normal distribution and calculations
Topic 4—Statistics and probability

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