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

Suppose only 75% of all drivers in a certain state regularly wear aseat belt. A random sample of 500 drivers is selected. What is theprobability that

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).

## Answer This Question

## Related Questions

- Statisics - transportation officials tell us that 80% of drivers wear seat belt ...
- statistics - twenty percent of drivers drining between 11pm and 3am are drunken ...
- drivers ed test - 3. one way the national highway safety act helps drivers ...
- Math - About 190 million drivers are registered in the United States. While on a...
- probability and statistics - the average age for licensed drivers in the country...
- statistics - A recent report stated "Based on a sample of 250 truck drivers, ...
- statistics - The average age for licensed drivers in the county is μ 40.3...
- statistics - The average age for licensed drivers in a county is ยต= 42.6, σ...
- Stats - A car insurance company has determined that 7% of all drivers were ...
- Stat - 6% of american drivers read the newspaper while driving if 300 drivers ...

More Related Questions