ENV 250 Module Five Homework: Statistical Analyses
1. Report the mean, median, and mode for the following data set of worm lengths measured in centimeters: 6, 4, 11, 12, 13, 9, 10, 14, 8, 4, 7, 12
2. Mr. Jones gave an exam to his environmental science class. The students earned the following grades: 45, 50, 55, 55, 60, 60, 65, 65, 65, 65, 65, 75, 75, 80, 85, 85, 85, 85, 85, 85, 90, 90, 95,100. Mr. Jones graphed the class’s scores.
What is the best measure of central tendency for Mr. Jones’s grade distribution? How should Mr. Jones report it?
3. A real estate agent has been given 10 houses to list. The house prices in dollars are:
110,000
95,000
87,000
92,000
99,000
250,000
265,000
210,000
275,000
240,000
A potential buyer calls and asks about house prices in the area. What measure of central tendency would best describe this data set? How should the real estate agent report it?
4. Matthew collected the following data:
Table 4.1 Effect of Diazinon Exposure on Tadpole Length
Tadpole length (cm)
Control 0.25 ppb 0.5 ppb 1.0 ppb
Tadpole 1 4.4 4.4 3.1 3.5
Tadpole 2 4.6 3.5 3.4 3.1
Tadpole 3 4.2 3.8 3.7 2.8
Tadpole 4 3.8 4.2 4.0 3.3
Tadpole 5 4.3 4.1 3.3 2.6
Mean (cm) 4.26 4.0 3.5 3.06
Std Dev (cm) 0.3 0.4 0.4 0.4
t-test probability
(p-value) NA 0.122 0.003 0.0002
Based on the data presented in the table above, are any of the treatment groups significantly different from the control group? If so, which groups are different and how do you know they are different?
5. Natalie conducted a study on the effects of triclosan on three algae populations. She collected an algae sample from three different ponds, counted the number of algae cells present in the sample, and then exposed them to a 5 ppm aqueous solution of triclosan and re-counted the number of algae cells in each sample. Using a paired t-test, she obtained a p-value of 0.083 when comparing the original algae population sizes to the population sizes after exposure to triclosan. Natalie concluded that triclosan is toxic to algae because her data for the three samples showed a trend toward a reduction in population size. What could Natalie do to show a statistically significant effect of triclosan on algae population size?
