How many bulbs be tested for estimate of the mean

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Reference no: EM13115846

An electrical firm that manufactures a certain type of lightbulb wants to estimate its mean life. Assuming that the life of the lightbulb is normally distributed and the standard deviation is known to be 40 hours, how many bulbs should be tested so that we can be 90% confident that the estimate of the mean will not differ from the true mean life by more than 10 hours?

Reference no: EM13115846

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