chapter 1112 frappy #1 - isd 622 · chapter 1112 frappy explained.notebook 6 march 27, 2014 chapter...
TRANSCRIPT
Chapter 1112 Frappy explained.notebook
1
March 27, 2014
Chapter 1112 Frappy #1
The pvalue of 0.0761 measures the probability of observing a difference between the two sample proportions as large as or larger than the one observed, if the survival rates for the two treatments (CC alone and CC + MMR) are in fact the same.
Need all 3 parts for essentially correct.
Because the pvalue of 0.0761 is greater than 0.05, the null hypothesis should not be rejected. That is, there is not sufficient evidence to conclude that the treatment “CC alone” produces a higher survival rate than the standard treatment “CC + MMR.”
Need to state conclusion and how the pvalue compares to alpha for essentially correct
Because the null hypothesis was not rejected, a Type II error could have occurred. A possible consequence is that CC + MMR would continue as the accepted practice when, in fact, CC alone would result in a higher survival rate.
Need a correct type and consequence for essentially correct.
*Note: don't get carried away with consequences. (not everything leads to death!)
Chapter 1112 Frappy explained.notebook
2
March 27, 2014
Chapter 1112 Frappy #2
100 patients
Group 150 patients
Group 250 patients
Treatment 20 mins music
Treatment20 mins quiet
Treatment 20 mins music
Treatment20 mins quietra
ndom
assignm
ent
allow time to pass
for random assignment: put numbers 1100 into a hat and draw out 50 without replacement. These are group 1 and the rest are group 2
Matched pairs design (each person gets both treatments)
Compare BP after each treatment
Type I error: Concluding that soothing music does reduce mean diastolic blood pressure compared to sitting quietly, when in fact it does not. The consequence of this type of error is that the clinic will offer music therapy when it is not effective. Type II error: Soothing music does reduce diastolic blood pressure compared to sitting quietly, but we fail to detect this and conclude that it does not. The consequence of this type of error is that the clinic will choose not to offer music therapy when it would have been effective. Which type of error is more serious? A case can be made for either type of error, and the student can take either side as long as a reasonable justification is given. For example, the student can say a Type I error is more serious because it will cost the clinic money with no benefit, or the student can say that a Type II error is more serious because the clinic will miss an opportunity to improve the health and wellbeing of its patients.
Chapter 1112 Frappy explained.notebook
3
March 27, 2014
Chapter 1112 Frappy #3
Ho: p=0.5Ha: p≠0.5
Because the sample size is small, the Normal curve is not a good approximation8(0.5)≯10
Increase the sample size.This will:
• decrease the variation which could make the same statistic significant.
• increases the power of the test• reduce the probability of making a type II error.
Chapter 1112 Frappy explained.notebook
4
March 27, 2014
Chapter 1112 Frappy #4
The width of the confidence interval depends on the sample size. The sample sizes need to be the same in order to have the 95% confidence intervals the same with for the same sample proportion. You could use a stratified sample design to randomly select 250 from each of the 8 groups.
Chapter 1112 Frappy explained.notebook
5
March 27, 2014
Chapter 1112 Frappy #5
Chapter 1112 Frappy explained.notebook
6
March 27, 2014
Chapter 1112 Frappy #6
approx. normal by CLT
A confidence interval is closely linked to a twosided hypothesis test. If you took the adjusted the pvalue to a twosided test, the pvalue would be 0.066 which would not be convincing evidence. This would now agree with the conclusion of the confidence interval.
Chapter 1112 Frappy explained.notebook
7
March 27, 2014
Chapter 1112 Frappy #7
p = percent of cars of this make and model that have the defect
Ho: p=0.05Ha: p>0.05
Type I error would occur if the firm takes the lawsuit when in fact only 5 percent of the cars have the defect. The consequences of this error would be the firm would incur more expenses than they collect from the manufacturer.
Type II error would occur if the firm does not take the lawsuit when in fact more than 5 percent of the cars have the defect. The consequences of this error would be the firm misses out on potential profit from a large lawsuit.
Chapter 1112 Frappy explained.notebook
8
March 27, 2014
Chapter 1112 Frappy #8
sketch of NPP is even better