d.  bought the equipment one-half month ago. 
e.  none of the above 

12.  A researcher is studying students in college in California.  She takes a sample of 400 students from 10 

colleges.  The average age of all college students in California is  
a. a 

statistic. 

b. a 

parameter. 

c. the 

median. 

d. a 

population. 

e.  none of the above 

13.  A sample of 150 new cell phones produced by Yeskia found that 12 had cosmetic flaws.  A 90% confidence 

interval for the proportion of all new Yeskia phones with cosmetic flaws is 0.044 to 0.116.  Which statement 
below provides the correct interpretation of this confidence interval?  
a.  There is a 90% chance that the proportion of new phones that have cosmetic flaws is 

between 0.044 and 0.116. 

b.  There is at least a 4.4% chance that a new phone will have a cosmetic flaw. 
c.  A sample of 150 phones will have no more than 11.6% with cosmetic flaws. 
d.  If you selected a very large number of samples and constructed a confidence interval for 

each, 90% of these intervals would include the proportion of all new phones with cosmetic 
flaws. 

e.  none of the above 

14.  The standard deviation of a normal population is 10.  You take a sample of 25 items from this population and 

compute a 95% confidence interval.  In order to compute the confidence interval, you will use 
a.  the t table because the degrees of freedom will be 24. 
b.  the t table because you have estimated the standard deviation from the sample. 
c.  the z table because the population standard deviation is known. 
d.  the z table because the sample size is small. 
e.  none of the above 

15.  You are conducting a one-sided test of the null hypothesis that the population mean is 532 versus the 

alternative that the population mean is less than 532.  If the sample mean is 529 and the p-value is 0.01, which 
of the following statements is true? 
a.  There is a 0.01 probability that the population mean is smaller than 529. 
b.  The probability of observing a sample mean smaller than 529 when the population mean is  

532 is 0.01. 

c.  There is a 0.01 probability that the population mean is smaller than 532. 
d.  If the significance level is 0.05, you will accept the null hypothesis. 
e.  none of the above 

16.  Half of the observations in a data set are greater than the  

a. mean. 
b. median. 
c. mode. 
d. standard 

deviation. 

e.  none of the above