In a study conducted at Virginia Tech on the development of

In a study conducted at Virginia Tech on the development of ectomycorrhizal, a symbiotic relationship between the roots of trees and a fungus, in which minerals are transferred from the fungus to the trees and sugars from the trees to the fungus, 20 northern red oak seedlings exposed to the fungus Pisolithus tinctorus were grown in a greenhouse. All seedlings were planted in the same type of soil and received the same amount of sunshine and water. Half received no nitrogen at planting time, to serve as a control, and the other half received 368 ppm of nitrogen in the form of NaNO₃. The stem weights, in grams, at the end of 140 days were recorded as follows:

No Nitrogen                          Nitrogen

                                                      .32                                               .26

                                                      .53                                               .43

                                                      .28                                               .47

                                                      .37                                               .49

                                                      .47                                               .52

                                                      .43                                               .75

                                                      .36                                               .79

                                                      .42                                               .86

                                                      .38                                               .62

                                                      .43                                               .46

For the above study, carry out an appropriate statistical analysis that will help address the research interests of the researchers above based on this data. Summarize your analysis and conclusions in a couple paragraphs. Be sure to:

Name the test you conduct

Mention any assumptions on which the test you conduct is based

Describe how you conducted the test (i.e. mention null and alternative hypotheses, decision rule, report test statistic, critical value, alpha, degrees of freedom)

Include descriptive statistics (means, standard deviations)

Summarize your statistical conclusion in the words of the problem as precisely as possible (describe the direction of effect, and be specific about contextualizing the result… in other words, don’t overgeneralize!)

Speculate on the implications of the statistical analysis for the research questions/interests of the researchers

Solution