| Date | None Specimen | Marks available | 3 | Reference code | SPNone.2.sl.TZ0.3 |
| Level | SL only | Paper | 2 | Time zone | TZ0 |
| Command term | Question number | 3 | Adapted from | N/A |
Question
A random variable X is distributed normally with mean 450. It is known that P(X>a)=0.27P(X>a)=0.27 .
Represent all this information on the following diagram.
[3]
a.
Given that the standard deviation is 20, find a . Give your answer correct to the nearest whole number.
[3]
b.
Markscheme
A1A1A1 N3
Note: Award A1 for 450 , A1 for a to the right of the mean, A1 for area 0.27 .
[3 marks]
a.
valid approach M1
e.g. P(X<a)=1−P(X>a)P(X<a)=1−P(X>a) , 0.73
a=462.256…a=462.256… A1
a=462a=462 A1 N3
[3 marks]
b.
Examiners report
[N/A]
a.
[N/A]
b.
