The standard error of the sample mean is equal to 5 when n=25.

The standard error of the sample mean is equal to 5 when n=25. If the sample size increases by a factor of four, how will the standard error change?

 A.   It will be cut to ¼ of 5 

 B.   It will quadruple 

 C.   It will be cut in half 

 D.   It will double 

Solution

The use of the student’s t distribution requires which of the following assumptions?

The use of the student’s t distribution requires which of the following assumptions?

 A.   The population is normal 

 B.   The sample is drawn from a positively skewed distribution 

 C.   The population variance is known 

 D.   The sample size is greater than 30 

Solution

The expected value of the sampling distribution of the sample mean

The expected value of the sampling distribution of the sample mean equals the population mean

 A.   when the population size N > 30. 

 B.   for all populations. 

 C.   when the population is symmetric. 

 D.   when the population is normally distributed. 

Solution

A random sample of 25 observations is selected from a normally distributed population.

A random sample of 25 observations is selected from a normally distributed population. The sample variance is 10. In the 95% confidence interval for the population variance, the upper limit will be 

 A.  17.331 

 B.  19.353 

 C.  6.097 

 D.  17.110 

Solution

A study of 200 insomniacs paid for by the Serta Mattress Company

A study of 200 insomniacs paid for by the Serta Mattress Company found that the average insomniac counted 350 sheep before falling asleep, with a standard deviation of 120. An insomniac is a person who has difficulty falling asleep. Some useful numbers might be:

=NORMSINV(0.89) 1.2265 

=NORMSINV(0.945) 1.5982 

=TINV(0.89,199) 0.1385 

=TINV(0.11,199) 1.6053 

=TINV(0.055,199) 1.9302 

Solution

Calculate an 89% confidence interval for the true mean number of sheep counted by insomniacs

Calculate an 89% confidence interval for the true mean number of sheep counted by insomniacs

 A.  350±13.62 

 B.  350±13.56 

 C.  350±16.38 

 D.  350±10.41 

 

Solution

To tell if the standard deviation of a process has changed, the control charts used are

 To tell if the standard deviation of a process has changed, the control charts used are

 A.  R and S charts. 

 B.  p and R charts. 

 C.  S and x bar charts. 

 D.   x bar and p charts

Solution