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Date May 2019 Marks available 2 Reference code 19M.1.SL.TZ1.T_11
Level Standard Level Paper Paper 1 Time zone Time zone 1
Command term Find Question number T_11 Adapted from N/A

Question

Consider the following graphs of normal distributions.

At an airport, the weights of suitcases (in kg) were measured. The weights are normally distributed with a mean of 20 kg and standard deviation of 3.5 kg.

In the following table, write down the letter of the corresponding graph next to the given mean and standard deviation.

[2]
a.

Find the probability that a suitcase weighs less than 15 kg.

[2]
b.

Any suitcase that weighs more than k  kg is identified as excess baggage.
19.6 % of the suitcases at this airport are identified as excess baggage.

Find the value of k .

[2]
c.

Markscheme

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

 (A1)(A1)  (C2)

Note: Award (A1) for each correct entry.

[2 marks]

a.

  (M1)

Note: Award (M1) for sketch with 15 labelled and left tail shaded OR for a correct probability statement, P(X < 15).

0.0766  (0.0765637…, 7.66%)      (A1)   (C2)

[2 marks]

b.

 (M1)

Note: Award (M1) for a sketch showing correctly shaded region to the right of the mean with 19.6% labelled (accept shading of the complement with 80.4% labelled) OR for a correct probability statement, P(X > k ) = 0.196 or P(X k ) = 0.804.

23.0 (kg)  (22.9959… (kg))      (A1)   (C2)

[2 marks]

c.

Examiners report

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

Syllabus sections

Topic 4—Statistics and probability » SL 4.9—Normal distribution and calculations
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Topic 4—Statistics and probability

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