Kevin uses his mobile phone for X minutes each day. X is a random variable which may be
modeled by a normal distribution with mean 28 minutes and standard deviation 8 minutes.
(a) Find the probability that on a particular day Kevin uses his mobile phone for :
(i) Less than 30 minutes (3 marks)
(ii) Between 10 and 20 minutes (4 marks)
(b) Find the probability that on 7 randomly selected days the mean time Kevin spends on
his mobile phone is at least 30 minutes. (4 marks)
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Kevin is the don't no solve yourself
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