In the study, 19 paraplegic dogs were injected with polyethylene glycol, or PEG-a nontoxic liquid polymer composed of lo

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In the study, 19 paraplegic dogs were injected with polyethylene glycol, or PEG-a nontoxic liquid polymer composed of long strings of the same type of molecules found in antifreeze. Within eight weeks, 13 of the 19 canines, about 68 percent, regained the use of their hind legs and were able to walk, some almost as well as before their injury. The dogs were injected twice with PEG, first soon after their owners brought them to the researchers' labs and then after standard surgery and steroids to reduce inflammation. Among a group of 24 dogs that received just the standard surgery and rehabilitation therapies, only about 25 percent regained the same level of mobility, feeling and bodily functions, with about 62 percent remaining paraplegic. Though the sample size is small the 68% success rate of this experimental treatment is definitely statistically significant when compared to the 25% success rate of the control group. Richard Borgens, the Purdue professor of neuroscience who oversaw the study, said his West Lafayette, Indiana lab had previously used PEG to repair damaged spinal cords in guinea pigs with about a 90 percent success rate. His team has even fused severed guinea pig spinal cords using PEG, although the dogs in the study had spinal disc ruptures that crushed, but did not sever, their spinal cords. Although exactly how PEG works remains unclear, Borgens said it appears to act as a sort of "molecular Band-Aid" that forms a temporary seal over breaches in nerve cells in the spinal cord, aiding their healing process. "This stuff is kind of like a radiator stop-leak for the nervous system. The polymer spreads out and forms a seal over the damaged areas in the nerve cells and allows the membrane below to reconstruct itself," said Borgens, director of Purdue's Center for Paralysis Research. He said PEG also appears to prevent secondary tissue death that often causes more damage than the original injury. Borgens said the agent only covers damaged cells and tissues when injected into the blood stream. The higher success rate in (literal) guinea pigs as compared to canines is an indication that this treatment works best in vertebrates with relatively simple nervous systems. In other words, it would presumably be less-effective in the incredibly complex nervous system of humans than it would be in any other animal. Still, this clearly deserves more study, and offers fresh hope for those who suffer from paraplegia. Let's keep our fingers crossed on a real breakthrough here.

Read the article about the new treatment then answer the following questions. Please type your responses (other than calculations). Include your first and last name. 1. Briefly describe what the experimental treatment is using complete sentences. (2 points) 2. Let p represent the proportion of dogs that regain the use of their legs. a. How many dogs are in the experimental group (PEG treatment)? (1 point) b. Find a point estimate for the proportion of dogs that regain the use of their legs with the PEG treatment. (1 points) c. Find a 95% confidence interval for the proportion of dogs that regain the use of their legs with the PEG treatment. Show your calculations below. Include the parameter being estimated in your interval. (2 points) d. Write a brief statement on the meaning of your confidence interval. (2 points)

e. Is the normal approximation to the binomial justified in this case? Explain. (1 point) 3a. How many dogs are in the control group (standard treatment)? (1 point) b. Find a point estimate for the proportion of dogs that regain the use of their legs with the standard treatment. (1 point) C. Find a 95% confidence interval for the proportion of dogs that regain the use of their legs with the standard treatment. You may use your calculator. (2 points) d. Write a brief statement on the meaning of your confidence interval. (2 points) e. Is the normal approximation to the binomial justified in this case? Explain. (1 point)

4. Compare the two confidence intervals. Do you think the new PEG treatment is significantly better than the standard treatment? Explain by comparing the confidence intervals. Is there any overlap? (2 points) 5. Use information in the article for a hypothesis test of a difference in proportions. The article claims that the difference between the 68% rate and the 25% success rate is statistically significant. Is this true? Use a 1% level of significance. Let p, represent the proportion of all dogs that would recover given the experimental treatment. Let P, represent the proportion of all dogs that would recover given the standard treatment State the two hypotheses. (2 points) H H: Use your calculator to find the sample test statistic. (2 points) What did you enter?x, = = n, What is the p-value of the test? (2 points)

ogs given the experimental treatment. Let p represent the proportion of all dogs that would recover given the standard treatment. State the two hypotheses. (2 points) Ho He: Use your calculator to find the sample test statistic. (2 points) What did you enter? x, = n = What is the p-value of the test? (2 points) Do you reject or fail to reject the null hypothesis? Explain. (2 points) What is your conclusion about the use of PEG? (2 points)