Question

1. Which formula gives the standard error for all xbar values?  _______

a) σ/√n b) σ   c) npq d) pq/n e) 1.96σ/√n

2. Prof. Gersch knows that the score on a standardized test is perfectly normal with a mean
of 200 and a standard deviation of 40.  He then takes a random sample of 16 tests.

Prof Gersch wants to check the probability that the average of these 16 tests is less than 210.
Which of these is equivalent to the probability that he is seeking?
a) P(z < 0.25)   b) P(z < 1.00) c) P(z < 4.0 0)     _______
d) P(0 < z < 0.25) e) P(0 < z < 1.00) f) c) P(0 < z < 4.00)

3. The Central Limit Theorem (CLT) deals primarily with the distribution of the:     _______
a) population mean
b) sample mean
c) sample proportion
d) sample median
e) sample variance

4-6. Prof. Gersch knows that the score on a standardized test is perfectly normal with unknown mean and a standard deviation of 50.  He then takes a random sample of 25 tests and finds that the average of these is 200.
4. Prof. Gersch wishes to make a 95% confidence interval for the average of all the grades.
What is the upper end of the confidence interval?

a) 298 b) 300 c) 219.6 d) 220   e) 225.8     f) 329     _______

5. How many exams should he sample so that the maximum margin of error
for his 95% confidence interval is 10?:     _______
a) 10 b) 100 c) 96 d) 97     e) 98  

6. If Prof. Gersch instead wants to make his 95% CI wider, he should:     _______
a) increase the z value
b) decrease the z value
c) decrease the sample size
d) increase the sample size
e) none of the above

Answer 1