1. Significance Test for a Mean
Section 9.2 Day 3
Significance Test for a Mean

2. Page 581, Activity 9.2a

3. Page 581, Activity 9.2a
1. Still being guided by shape, center, and spread, the strongest evidence for a “significant” difference would be a plot that shows:

4. Page 581, Activity 9.2a
1. Still being guided by shape, center, and spread, the strongest evidence for a “significant” difference would be a plot that shows:
a nearly symmetrical distribution

5. Page 581, Activity 9.2a
1. Still being guided by shape, center, and spread, the strongest evidence for a “significant” difference would be a plot that shows:
a nearly symmetrical distribution
with a positive center (greater than 0)

6. Page 581, Activity 9.2a
1. Still being guided by shape, center, and spread, the strongest evidence for a “significant” difference would be a plot that shows:
a nearly symmetrical distribution
with a positive center (greater than 0)
small variation

7. Page 581, Activity 9.2a
1. Still being guided by shape, center, and spread, the strongest evidence for a “significant” difference would be a plot that shows:
a nearly symmetrical distribution
with a positive center (greater than 0)
small variation
and interval does not contain 0

8. Page 581, Activity 9.2a Plot that shows:
a nearly symmetrical distribution
with a positive center (greater than 0)
small variation
and interval does not contain 0
Experiment B fits this description.

9. Page 581, Activity 9.2a
2. Rank from strongest to weakness evidence:

10. Page 581, Activity 9.2a 2. Rank from strongest to weakness evidence: B
Experiment B gives strongest evidence for previous reasons.

11. Page 581, Activity 9.2a
2. Rank from strongest to weakness evidence: B, D, C,
Experiment B gives strongest evidence for previous reasons.
Experiment D gives slightly stronger evidence than does C because boxplot D shows a slightly higher center and a little less spread.

12. Page 581, Activity 9.2a
2. Rank from strongest to weakness evidence: B, D, C, A
Experiment A shows no conclusive evidence of an increase because its center is near 0 and it has tremendous spread compared to the others.

13. Page 581, Activity 9.2a
3. What else would you like to know about these data, in addition to what you see in the boxplots, in order to improve your inference-making ability?

14. Page 581, Activity 9.2a
3. Knowing sample size and design of experiment (matched pairs or repeated measures) would improve inference making ability

15. Page 581, Activity 9.2a
3. Knowing sample size and design of experiment (matched pairs or repeated measures) would improve inference making ability

16. Page 581, Activity 9.2a
3. Knowing sample size and design of experiment (matched pairs or repeated measures) would improve inference making ability
Provides blocking which helps reduce what?

17. With-in treatment variability
Page 581, Activity 9.2a
3. Knowing sample size and design of experiment (matched pairs or repeated measures) would improve inference making ability
Provides blocking which helps reduce what?
With-in treatment variability

18. Page 597, P23

19. Page 597, P23
a) The alternative hypothesis should be one-sided because the claim (research or alternative hypothesis) is that the mean price increased.

20. Page 597, P23
b) x = mean selling price for a sample of houses sold in Gainesville this month

21. Page 597, P23
b) x = mean selling price for a sample of houses sold in Gainesville this month
= true mean selling price of all houses sold in Gainsville for this month

22. Page 597, P23 c)
H0: mean selling price of all houses sold in Gainsville for this month is the same as the mean for last month

23. Page 597, P23 c)
H0: mean selling price of all houses sold in Gainsville for this month is the same as the mean for last month
Ha: mean selling price of all houses sold in Gainsville for this month is greater than the mean for last month

24. Your grade in your statistics class is not all what you had hoped it would be. You took five exams, each worth 100 points. Your scores were 52, 63, 72, 41, and 73.
Your teacher averages these scores, gets 60.2, and says you have earned a D.

25. You think what you have learned about a confidence interval for a mean can help you convince your teacher to give you a C, which is a mean score between 70 and 79.

26. You remember that your teacher told your class at the beginning of the year that the questions on the exams would be only a random sample of thousands of questions that he could ask.
Write an explanation that supports your argument that you should receive a C rather than a D.

27. Your grade in your statistics class is not all that you had hoped it would be. You took five exams, each worth 100 points. Your scores were 52, 63, 72, 41, and 73. Your teacher averages these scores, gets 60.2, and says you have earned a D. You think what you have learned about a confidence interval for a mean can help you convince your teacher to give you a C, which is a mean score between 70 and 79. You remember that your teacher told your class at the beginning of the year that the questions on the exams would be only a random sample of the thousands of questions that he could ask. Write an explanation that supports your argument that you should receive a C rather than a D.

28. Conditions
(1) Randomness: scores on the 5 exams can be considered random sample as the questions on the exams were a random sample that could be asked.

29. Conditions
(1) Randomness: scores on the 5 exams can be considered random sample as the questions on the exams were a random sample that could be asked.
(2) Normality: boxplot shows fairly symmetric pattern with no outlier so reasonable to assume sample came from normally distributed population

30. Conditions
(3) Population size: population is thousands of questions so population is at least 10 times the sample size

31. 95% CI: (43.234, )

32. 95% CI: (43.234, )
A population mean from 70 to is reasonably likely to have produced results like these test scores.

33. 95% CI: (43.234, )
A population mean from 70 to is reasonably likely to have produced results like these test scores.
Therefore, the student could plausibly be a C student in stats.

34. Questions?
Quiz
both sides of a note card