A psychology instructor introduced some modifications to her teaching methods, and would like to know how effective they are. She teaches 2 sections: one section includes these modifications, while the other does not. She compared the scores on a standardized test for the 278 students in her modified section with the scores of the 320 students in her regular section. The following 99% confidence interval was obtained for_{modifiedregular}:

(-0.28, 5.88).

(a) What is the margin of error for this interval? (use 3 decimals)

(b) If a 98% confidence interval were computed, how would the margin of error be affected?

The margin of error for 98% confidence would be

---

greater

smaller

than for 99% confidence. As confidence decreases, the margin of error

---

increases

decreases

.

(c) Does the original 99% confidence interval enable us to conclude that students who learn psychology with these modified methods will have higher mean scores than those with regular methods?

---

Yes

No

, because the interval

---

does not contain 0

contains 0

, there is

---

sufficient evidence

insufficient evidence

to conclude that students who learn psychology with the modified methods have a higher mean score than those with the regular method.

(d) Explain what the 99% confidence interval means:

With 99% confidence, a randomly selected student in the modified section is expected to score between 0.28 points lower and 5.88 points higher than a randomly chosen student in the regular section.

99% of students in the modified section are expected to score between 0.28 points lower and 5.88 points higher than students in the regular section.

With 99% confidence, the mean score for students in the modified section is expected to be between 0.28 points lower and 5.88 points higher than the mean score for students in the regular section.

There is 99% confidence that all students in the modified section will score between 0.28 points lower and 5.88 points higher than students in the regular section.

(e) If a hypothesis test were done to determine if the scores were different, what does the above 99% confidence interval imply about the P-value?

The P-value would be

---

greater

less

than

---

0.01

0.02

0.05

0.10