The life of headlamp bulbs is normally distributed with a mean of 300 hours and a standard deviation of 15 hours. Determine the range of 80% of the headlamp bulbs

Question

e.mccormick · Answer

Do you know how to use a normal distribution table?

anonymous · Answer

yes kind of

e.mccormick · Answer

So what would the z score be for 80%?  Start with that.

e.mccormick · Answer

See, once you know the SD, you have the fact that 1SD=15 hours.  So whatever the SD will be, you can say $300\pm z15$

anonymous · Answer

okay ....

e.mccormick · Answer

Do you have a z score table in your book?

anonymous · Answer

yes

e.mccormick · Answer

Did you look it up?  Ay issues?  your .... seems like you were unsure about something still.