1.When the value of the standard deviation increases, the valueof the z score will generally tend to

a. increase

b. decrease

2. In a standard normal distribution, what z-scorecorresponds to the 75th percentile?

a. z=.67

b. z=.07

c. z=.75

d. z=1.75

3. The total area under the normal curve is approximately 1.

a. true

b. false

4. If IQ scores are normally distributed with a mean of 100 anda standard deviation of 20, then the probability of a person's havean IQ score of at least 130

a. is does not exist

b. .0668

c. is .4332

d. is .5000

5. The life of a brand of battery is normally distributed with amean of 2 hours and a standard deviation of 6 hours. Theprobability that a single randomly selected battery lasts more than70 hours is

a. .0000

b. .0918

c. .4082

d. .9082

6. Suppose family incomes in a small town are normallydistributed with a mean of $1200 and a standard deviation of $600per month. The probability that a given family has an incomebetween $1000 and $2050 per month is

a. .0918

b. .4082

c. .9082

d. .5515

7. Suppose family incomes in a small town are normallydistributed with a mean of $1200 and a standard deviation of $600per month. The probability that a given family has an income up to$2,000 per month is

a. .9082

b. .0918

c. .4082

d. .5515

8. The normal distribution is centered at its mean.

a. true

b. false