Mathematics 9709 · AS & A Level · The normal distribution
The normal distribution — practice question
Karli's daily time on social media, measured in minutes, follows a normal distribution with mean 125 and standard deviation 24.
(a(i))[5]
Out of 365 days in the year, on how many would you expect Karli to spend more than 142 minutes on social media?
(a(ii))[3]
Find the chance that Karli spends more than 142 minutes on social media on fewer than 2 of 10 days chosen at random.
(b)[3]
On $90\%$ of days, Karli spends more than $t$ minutes on social media. Determine $t$.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correct standardisation written as $P(Z>\frac{142-125}{24})$.” …