binomial distribution question

[lizzpalmer]

The results of the 2007 National Survey on Drug Use and Health found that among young adults ages 18-25, in the last month, 16.4% had used marijuana; 1.7% had used cocaine; 6.0% had abused prescription drugs. If we select 1000 young adults at random, approximate the probability of the given event.

1. Less than 150 had used marijuana
2. Between 12 and 25 had used cocaine
3. More than 50 had abused prescription drugs

If someone could help me with this I'd appreciate it. It is due sunday night.

thanks lizz

 

[tkhunny]

I'm not sure I would stick entirely with the Binomial on this one.

Expected number of MJ users: 1000 * 0.167 = 167
Variance of MJ users: 1000 * 0.167 * 0.833 = 139.11

Now use a Normal Approximation to answer the question on MJ.

z = (150-167)/sqrt(139.11)

Let's see what you get for all three based on this tachnique.