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
