Date | May 2017 | Marks available | 2 | Reference code | 17M.1.sl.TZ2.3 |
Level | SL only | Paper | 1 | Time zone | TZ2 |
Command term | Find | Question number | 3 | Adapted from | N/A |
Question
The random variable X is normally distributed with a mean of 100. The following diagram shows the normal curve for X.
Let R be the shaded region under the curve, to the right of 107. The area of R is 0.24.
Write down P(X>107).
[1]
a.
Find P(100<X<107).
[3]
b.
Find P(93<X<107).
[2]
c.
Markscheme
P(X>107)=0.24(=625, 24%) A1 N1
[1 mark]
a.
valid approach (M1)
egP(X>100)=0.5, P(X>100)−P(X>107)
correct working (A1)
eg0.5−0.24, 0.76−0.5
P(100<X<107)=0.26(=1350, 26%) A1 N2
[3 marks]
b.
valid approach (M1)
eg2×0.26, 1−2(0.24), P(93<X<100)=P(100<X<107)
P(93<X<107)=0.52(=1325, 52%) A1 N2
[2 marks]
c.
Examiners report
[N/A]
a.
[N/A]
b.
[N/A]
c.