Giant Tarantulas. A tarantula has two body parts. The anterior part of the body is covered above by a shell, or carapace.

In the paper “Reproductive Biology of Uruguayan Theraphosids”

(The Journal of Arachnology, Vol. 30, No. 3, pp. 571–587), F. Costa and F. Perez–Miles discussed a large species of tarantula whose common name is the Brazilian giant tawny red. A simple random sample of 15 of these adult male tarantulas provided the following data on carapace length, in millimeters (mm). 15.7 18.3 19.7 17.6 19.0 19.2 19.8 18.1 18.0 20.9 16.4 16.8 18.9 18.5 19.5

a. Obtain a normal probability plot of the data.

b. Based on your result from part (a), is it reasonable to presume that carapace length of adult male Brazilian giant tawny red tarantulas is normally distributed? Explain your answer.

c. Find and interpret a 95% confidence interval for the mean carapace length of all adult male Brazilian giant tawny red tarantulas.

The population standard deviation is 1.76 mm.

d. In Exercise 6.97, we noted that the mean carapace length of all adult male Brazilian giant tawny red tarantulas is 18.14 mm. Does your confidence interval in part

(c) contain the population mean?

Would it necessarily have to? Explain your answers.