Chapter 7, Problem AP2.24CPT

(a)

To determine

To Explain: a few sentences comparing the distribution of seed mass for the two groups of plants.

Answer to Problem AP2.24CPT

Skewed with the same centre and a higher spread for the cicada plants

Explanation of Solution

Given:

  

  

By seeing the distribution, it is observed that the distribution of the cicada plants is slightly skewed to the right, where the distribution of the control plants is skewed to the left.

Centre: The median would be the same for both of the distributions, where the mean is slightly higher for Cicada Plants.

Spread: the cicada plants have a large spread, where the box plot is wider.

Outlines: neither distributions appears to contain outliers as there are no “ $x$ ’s in the box plots.

(b)

To determine

To find: the distribution likely has the larger mean.

Answer to Problem AP2.24CPT

Cicada plants group

Explanation of Solution

Given:

  

  

In the previous part (a), it is concluded that the control plants group contained more skewed. Since the mean is strongly influenced by skewed the mean is too more influenced by the left-skewed in the control plants distribution, since a left-skewed distribution contains unusually small values, these small values will decrease the mean and therefore the mean of the control plants group will be lower than the mean of the cicada plants group.

(c)

To determine

To Explain: the purpose of the random assignment in this study.

Answer to Problem AP2.24CPT

For the surety that the two groups are as similar as possible, prior to the experiment

Explanation of Solution

Given:

  

  

The random assignments to the groups ensure that the two groups are as similar as possible prior to the experiment and then it also knows that the results of the experiment are due to the treatments.

(d)

To determine

To Explain: the name one benefit and one drawback of only using American bellflowers in the study.

Answer to Problem AP2.24CPT

Advantage: differences between control group and treatment are small

Disadvantage: result of experiment cannot be generalized to other flowers.

Explanation of Solution

Given:

  

  

A benefit is that the differences between the treatment and control group will be very small, because all flowers will be of the same type.

A drawback is that you will only have data for one type of flower and therefore the results of the experiment could not be generalized to other flowers.