The lifetime of lightbulbs are normally distributed with a Mean = 5122 hours and standard deviation =234 hours. If we want to be sure that 98% of all bulbs last longer than advertised, what figure should be advertised?

This is to ask you to find a particular x-value so that P(X>x-value)= 0.9800

This can be converted as P(Z>(x-value - /))=0.9800 The value = 2.05