The number of absences per week by workers at a factory has the distribution $$$\operatorname{Po}(2.1)$$$. Find the probability that the number of absences in a 3-week period is more than 4 and less than 8. ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................

Mathematics

IGCSE&ALevel

CAIE

Exam No：9709_w20_qp_63 Year：2020 Question No：5(c)

Answer:

$\lambda=6.3$
$\mathrm{e}^{-6.3}\left(\frac{6.3^{5}}{5 !}+\frac{6.3^{6}}{6 !}+\frac{6.3^{7}}{7 !}\right)$
$=0.455(3 \mathrm{sf})$

6.1.1 use formulae to calculate probabilities for the distribution $\text { Po }(\lambda)$