| Date | November 2015 | Marks available | 2 | Reference code | 15N.2.sl.TZ0.2 |
| Level | SL only | Paper | 2 | Time zone | TZ0 |
| Command term | Find | Question number | 2 | Adapted from | N/A |
Question
The following table shows the probability distribution of a discrete random variable \(X\).
Find the value of \(k\).
[3]
a.
Find \({\text{E}}(X)\).
[2]
b.
Markscheme
evidence of using \(\sum {{p_i}} = 1\) (M1)
correct substitution A1
eg\(\;\;\;0.15 + k + 0.1 + 2k = 1,{\text{ }}3k + 0.25 = 1\)
\(k = 0.25\) A1 N2
[3 marks]
a.
correct substitution (A1)
eg\(\;\;\;0 \times 0.15 + 1 \times 0.25 + 2 \times 0.1 + 3 \times 0.5\)
\({\text{E}}(X) = 1.95\) A1 N2
[2 marks]
Total [5 marks]
b.
Examiners report
[N/A]
a.
[N/A]
b.
Syllabus sections
Topic 5 - Statistics and probability » 5.7 » Expected value (mean), \({\text{E}}(X)\) for discrete data.
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