Spinocerebellar ataxia type 1 is a neurodegenerative disease marked by the gradual loss of motor skills and culminating in early death. It is caused by an expanded CAG repeat  in the coding region of the Ataxin-1 gene. Fryer et al. (2011) investigated the possible beneficial effects of exercise in treating the disease. They used a mild exercise regimen in a mouse model of the disease (a mouse strain in which an expanded CAG repeat was “knocked in” to the mouse version of the same gene, and that had similar symptoms). The life spans (in days) are given below for six exercised mice and six mice not given the exercise regimen. The data and 95% confidence intervals are shown in the accompanying graph.

a. What type of graph is shown?

b. Using only the graph, is it possible to predict the outcome of a formal test of whether mean life span differs between the two treatments? Explain.

c. Test whether exercise affects life span in mice affected by the disease.

d. By how many days does exercise increase life span on average? Use a confidence interval to answer this question.

Transcribed Image Text:

No exercise: 240,240, 261,261, 271,271, 275,275, 276,276, 281281 Exercise: 261,261, 293,293, 316,316, 319,319, 324,324, 347347