17 The lifetime of Zaple smartphone batteries, \(X\) hours, is normally distributed with mean 8 hours and standard deviation 1.5 hours.
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- Find \(\mathrm { P } ( X \neq 8 )\)
17
- (ii) Find \(\mathrm { P } ( 6 < X < 10 )\)
17 - Determine the lifetime exceeded by \(90 \%\) of Zaple smartphone batteries.
17 - A different smartphone, Kaphone, has its battery's lifetime, \(Y\) hours, modelled by a normal distribution with mean 7 hours and standard deviation \(\sigma\).
25\% of randomly selected Kaphone batteries last less than 5 hours.
Find the value of \(\sigma\), correct to three significant figures.