Date | November 2019 | Marks available | 1 | Reference code | 19N.2.SL.TZ0.S_7 |
Level | Standard Level | Paper | Paper 2 | Time zone | Time zone 0 |
Command term | Show that | Question number | S_7 | Adapted from | N/A |
Question
The following table shows the probability distribution of a discrete random variable , where and .
Show that .
Find the difference between the greatest possible expected value and the least possible expected value.
Markscheme
correct approach A1
eg ,
AG N0
[1 mark]
correct substitution into (A1)
eg ,
valid attempt to express in one variable M1
eg , ,
,
correct value of greatest (A1)
(exact)
valid attempt to find least value (M1)
eg graph with minimum indicated, and
and if in terms of
and if in terms of
correct value of least (A1)
eg (exact)
difference (exact) A1 N2
[6 marks]