Question

1-Ientify appropriate analyses for the following data sets. For each example, identify one statistical method and one graphical method (2 points each):

a.You collect soil samples from 12 locations. At each location, you pulled out a 10 cm deep soil sample. You cut each sample in half and analyze both the top and bottom halves for lead (Pb). You want to know if the lead concentration in the bottom halves exceeds that in the top halves.

b.You have randomly collected 15 water samples each from three different cities. You measured nitrate concentration in each water sample. You know from examination of the data, that the nitrate concentrations are not normally distributed. You want to determine whether water nitrate concentrations vary among the different cities.

c.You have collected fish annually over 12 years, and you want to see how their tissue mercury concentration has changed over time.

d. You have surveyed a random population of people in Madison, St. Clair, Monroe, and St. Louis counties. There were at least 50 survey responses per county. Each survey participant indicated whether or not they believe in human-caused global climate change. You want to determine whether the frequency of believing in human-caused climate change is different among the different counties.

e.You are sampling open vs. forested plots for the presence or absence of a shrub species. You want to see if there is an association between plot type and shrub presence. The study examines 8 open and 8 forested plots in total.

Answer 1

(a) Statistical method = Paired t-test

Graphical method = Line graph

(b) Statistical method = Kruskal Wallis test

Graphical method = Boxplot

(c) Statistical method = Paired t-test

Graphical method = Line graph

(d) Statistical method = One sample t-test

Graphical method = Normal distribution curve

(e) Statistical method = Chi-square test

Graphical method = Chi-square plot

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