1. For a fixed confidence level, in stating a confidence-interval
estimate of a population mean, the level of confidence increases as the
size of the interval _____________ .a.increases b. decreases c. remains
unchanged d. not enough information to determine
2. Which of the following statements regarding t-curves is/are true?
A. The total area under a t-curve with 10 degrees of freedom is greater
than the area under the standard normal curve.
B. The t-curve with 10 degrees of freedom is flatter and wider than the
standard normal curve.
C. The t-curve with 10 degrees of freedom more closely resembles the
standard normal curve than the t-curve with 20 degrees of freedom.
A & B
A & C
B & C
A, B, C
Suppose that you wish to obtain a confidence interval for a population
mean. Under the conditions described below, should you use the
z-interval procedure, the t-interval procedure, or neither?
- The population standard deviation is known.- The population is not
normally distributed.- The sample size is 12.A. z-interval B. t-interval
4. A researcher wishes to estimate the mean resting heart rate for
long-distance runners. A random sample of 12 runners yields the
following heart rates, in beats per minute.
80 81 61 79 59 6680 62 72 78 60 63
Use the data to obtain a point estimate of the mean resting heart rate
for all long distance runners.
A.66.7 beats per minute B. 68.4 beats per minute C. 70.1 beats per
minute D. 71.9 beats per minute
5. A college statistics professor has office hours from 9:00 am to 10:30
am daily. A sample of waiting times to see the professor (in minutes) is
10, 12, 20, 15, 17, 10, 30, 28, 35, 28, 19, 27, 25, 22, 33, 37, 14, 21,
20, 23. Assuming
7.84 find the 95.44% confidence interval for the population mean.a. -3.5
to 3.5 minutes b. -7.7 to 7.8 minutes c. 18.8 to 25.8 minutes d. 19.5 to
6. Find the value of a which corresponds to a level of confidence of
a. 0.007 b. 0.07 c. 0.7 d. 0.93
7. The principal randomly selected six students to take an aptitude
test. Their scores were:79.3 81.3 71.4 89.6 89.2 76.3 Determine a 90%
confidence interval for the mean score for all students.
a. 75.17 to 87.20 b. 75.27 to 87.10 c. 87.10 to 75.27 d. 87.20 to 75.17
8. Suppose you have obtained a 95% confidence interval for . Which of
the following statements is/are true regarding the relationship between
precision and confidence level? Assume that the sample size is fixed.
A. Increasing the confidence level to 99% will result in a narrower
B. Decreasing the confidence level to 90% will result in greater
C. Decreasing the precision will result in a higher confidence level.
D. Increasing the precision will result in a higher confidence level.
A and C A and D B and C B and D
9. A sample of 45 eggs yields a mean weight of 1.37 ounces. Assuming
that o = 0.53 ounces, find the margin of error in estimating at the 95%
level of confidence.
a. 0.02 oz b. 0.13 oz c. 0.15 oz d. 6.71 oz
10. A population is normal with a variance of 51. Suppose you wish to
estimate the population mean Find the sample size needed to assure with
68.26 percent confidence that the sample mean will not differ from the
population mean by more than 4 units.
Hint: The VARIANCE is 51, so what is the standard deviation
a. 4 b. 11 c. 41 d. 163
11. For a t-curve with df = 11, find t0.10
a.1.280 b.1.363 c.1.372 d.2.718