The random variable X X\,X has the following probability distribution.
| xxx | 1 | 2 | 3 | 4 | 5 |
| P(X=x)P(X=x)P(X=x) | kkk | k2\displaystyle \frac{k}{2}2k | k3\displaystyle \frac{k}{3}3k | k4\displaystyle \frac{k}{4}4k | k5\displaystyle \frac{k}{5}5k |
where k k\,k is a constant.
Show that k=60137\displaystyle k = \frac{60}{137}k=13760
The random variables X1 X_1\,X1 and X2 X_2\,X2 are independent and each have the same distribution as XXX. Show that P(X1+X2=7)=0.0703P(X_1 + X_2 = 7) = 0.0703P(X1+X2=7)=0.0703 to 3 significant figures
215 exam-style questions on Edexcel A Level Maths Statistical Distributions, covering 6.1 Probability Distributions, 6.2 The Binomial Distribution, and 6.3 Cumulative Probabilities. Each one has a worked solution and a mark scheme showing where the marks go.