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jnl27 · Mar 26, 2009, 09:38 PM

I am having trouble with my homework. I have these 2 questions out of 20 that are giing me the most trouble. I just can't seem to figure out the answers.
Question 1
On an exam regarding compassion in police officers, exam averages were mu=76 and standard deviation= 12. The higher the score, the greater the compassion shown by officers. Officer A had a score of 68; Officer B had a score of 73; and Officer C had a z- score of z= -.50. Place the Officers in order, from lowest to highest.

Ouestion 2
You are a jury selection advisor. The government selects juries from the list of registered voters. The average age of registered voters in your district is mu= 39.7 years with a standard deviation of 11.8. The distribution of ages is approximatley normal.
What proportion of the jurors would you expect to be more than 55 years of age?
What porportion of the jurors would you expect to be less than 30 years of age?
A jury for a 1st degree murder trial has been drawn. The average age for theis jury is 60.5 years of age. What is the probability of obtaining a jury with this average age from the registered voter population?

galactus · Mar 27, 2009, 08:40 AM

Ouestion 2
You are a jury selection advisor. The government selects juries from the list of registered voters. The average age of registered voters in your district is mu= 39.7 years with a standard deviation of 11.8. The distribution of ages is approximatley normal.

What proportion of the jurors would you expect to be more than 55 years of age?

Use $z=\frac{x-{\mu}}{\sigma}$

$\frac{55-39.7}{11.8}=1.3$

Looking this up in the table we see it has proportion .9032.

Since we want greater than, subtract from 1. That's because z scores come from the left.

1-.9032=.0968.

About 9.68% of the jurors are older than 55.

If a problem says 'less than' just use the proportion you find in the table.

If the first problem would have said 'less than 55', then we would have just used the .9032.