The following data represent petal lengths (in cm) for independent random samples of two species of iris. 5.0 5.8 6.3 6.1 5.1 5.5 5.3 5.5 6.9 5.0 4.9 6.0 4.8 6.1 5.6 5.1 5.6 4.8 5.4 5.1 5.1 5.9 5.2...


The following data represent petal lengths (in cm) for independent random samples of two species of iris.














































5.05.86.36.15.15.55.35.56.95.04.96.04.86.15.65.1
5.64.85.45.15.15.95.25.75.44.56.45.35.56.75.74.9
4.85.95.15.1
















































1.61.61.41.51.51.61.41.11.21.41.71.01.71.91.61.4
1.51.41.21.31.51.31.61.91.41.61.51.41.61.21.91.5
1.61.41.31.71.51.7



(a)Use a calculator with mean and standard deviation keys to calculate x1,s
1, x2, ands
2. (Round your answers to four decimal places.)


x1=


s
1=

x2=


s
2=




(b)Let ?1 be the population mean forx
1 and let ?2 be the population mean forx
2. Find a 99% confidence interval for ?1 − ?2. (Round your answers to two decimal places.)


lower limit=__

upper limit=__




(c)Explain what the confidence interval means in the context of this problem. Does the interval consist of numbers that are all positive? all negative? of different signs? At the 99% level of confidence, is the population mean petal length ofIris virginica longer than that ofIris setosa?



A-Because the interval contains only positive numbers, we can say that the mean petal length ofIris virginica is longer.

B-Because the interval contains only negative numbers, we can say that the mean petal length ofIris virginica is shorter.

C-Because the interval contains both positive and negative numbers, we cannot say that the mean petal length ofIris virginica is longer.





(d)Which distribution did you use? Why?



A-The standard normal distribution was used because ?1 and ?2 are known.

B-The Student'st-distribution was used because ?1 and ?2 are unknown.

C-The Student'st-distribution was used because ?1 and ?2 are known.

D-The standard normal distribution was used because ?1 and ?2 are unknown.


Do you need information about the petal length distributions? Explain.


A-Both samples are large, so information about the distributions is not needed.

B-Both samples are small, so information about the distributions is needed.

C-Both samples are large, so information about the distributions is needed.

D-Both samples are small, so information about the distributions is not needed.



Jun 07, 2022
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