Answers for HW #2
STAT 554, Spring 2008
Print out this page, put your name on it, fill in the correct
answers, and submit it at our 6th class meeting.
(For some of the parts (which are worth no points), answers are provided.
These may serve as useful checks of your work.)
Problem 1
Round each confidence interval endpoint to the nearest tenth.
| part |
answer |
| (a) |
(61.2, 65.1) |
| (b) |
(61.6, 64.7) |
| (c) |
(60.1, 66.2) |
| (d) |
# add'l obs.
85 |
| |
conf. int.
(61.0, 62.0) |
Problem 2
Round the power value to the nearest thousandth.
Give the exact (integer) value for the sample
size requested for part (b).
| part |
answer |
| (a) |
0.240 |
| (b) |
126 |
(Note: For part (b), a sample size of 126 results in a power of about 0.801 and a sample size of 125 results in a
power of about 0.798. I gave full credit if you gave either 125 or 126 as your answer.)
Problem 3
Round each p-value
to two significant
digits,
and each confidence interval endpoint as indicated on the assignment.
| part |
answer |
| (a) |
0.067 |
| (b) |
0.079 |
| (c) |
(0.51, 0.96) |
| (d) |
(0.48, 0.99) |
| (e) |
(0.48, 0.90) |
| (f) |
(0.45, 0.92) |
| (g) |
(0.45, 0.92) |
Problem 4
Round each confidence interval endpoint as indicated on the assignment.
| part |
answer |
| (a) |
(0.477, 0.648) |
| (b) |
(0.473, 0.652) |
| (c) |
(0.476, 0.645) |
| (d) |
(0.472, 0.649) |
| (e) |
(0.472, 0.650) |
Problem 5, Problem 6, & Problem 7
Round each p-value to two significant
digits.
(E.g., the following numbers all have two significant digits:
0.029, 1.7, 0.0040, 0.33, 0.00062.)
Round each confidence interval endpoint as indicated on the assignment.
| Problem |
answer |
| 5 |
0.39 |
| 6 |
0.010 |
| 7 |
(83.0, 89.0) |
(Note: The p-value reported for 6 was obtained using the normal approximation. If you went to the trouble to
determine the exact p-value and reported 0.012 as your answer, full credit was given for that.)