A hint to get started
Packets, nested counts and a modal-parameter range
A manufacturer produces a large number of coloured glowing sticks, which are packed in packets of 8. Each packet consists of randomly chosen coloured glowing sticks. On average, 12% of the glowing sticks are green.
(i) Explain the significance of ‘large number’ in the first sentence.
(ii) Find the probability that a randomly chosen packet of glowing sticks contains at least 3 green glowing sticks.
(iii) Ian buys 40 randomly chosen packets of glowing sticks for a concert. Find the probability that fewer than 6 of these packets contain at least 3 green glowing sticks.
On average, the proportion of glowing sticks that are blue is . It is known that the modal number of blue glowing sticks in a packet is 3.
(iv) Use this information to find exactly the range of values that can take.
[2018/YJC/II/8]
CJC · Discussion · Question 9
For the nested model count qualifying packets; for the mode compare neighbouring binomial masses.