May 2, 2009 - Extra Credit Questions

BONUS CREDIT QUESTIONS - For each question you post in your work groups correctly, you will be given 1 extra point, for a possibility of 10 extra points.


1. A random sample of 200 high school seniors is given the SAT-V test. The mean score for
this sample is 483. Assuming that the population is normally distributed, the mean score
μ for all high school seniors will be:

a) 2.415
b) 200
c) 483

2. Given the same sample statistics, which level of confidence will produce the narrowest
confidence interval?

a) 75%
b) 85%
c) 90%
d) 99%

3. The margin of error is present only when the sample size is less than 30.
a) True
b) False

4. When a t-distribution is used to estimate a population mean, the degrees of freedom are
equal to one less than the sample size.

a) True
b) False

5. A t-distribution is used when the random variable is distributed normally, the sample size
is < 30 and the value of σ (sigma) is unknown.

a) True
b) False

6. The critical value that corresponds to a 95% confidence level is:

a) ±1.645
b) ±1.96
c) ±2.33
d) ±2.575

7. The point estimate is a single value estimate for a sample statistic.

a) True
b) False


8. The most unbiased point estimate of the population mean μ is the sample mean.

a) True
b) False

9. Which of the following statements describe the properties of a t-distribution?

a) The t-distribution is bell-shaped and symmetric about the mean.
b) The total area under a t-curve is 1 or 100%.
c) The mean, median, and mode of the t-distribution are equal to zero.
d) As the degrees of freedom decrease, the t-distribution approaches the normal distribution.

10. The critical value, tc, for c = 0.99 and n = 10 is:

a) 1.833
b) 2.262
c) 2.281
d) 3.250