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March 2, 2015

March 2, 2015

Posted by **Dre** on Thursday, October 21, 2010 at 11:11pm.

a). Between 360 and 400 (inclusive) of the drivers in the sampleregularly wear a seat belt?

b). Fewer than 400 of those in the sample regularly wear a seatbelt?

Part b)is what I am having a hard time with. This is what I did for part a).

using a Normal approximation:

z = (400.5-500*0.75) /

sqrt(500*0.75*0.25) = 2.63

z = (359.5-500*0.75) /

sqrt(500*0.75*0.25) = -1.60

these numbers correspond to areas of 0.9957 and 0.0548, so the probability is: 0.9957-0.0548 = 0.9409

I need help solving part b).

- statistics -
**Anonymous**, Wednesday, November 3, 2010 at 2:22amUse the same method you did for part a. Only now you are dealing with just an exclusive upper-bound. Just make sure you use the right correction factor and you should be set.

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