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 ni222 trogen at planting time, to serve as a control, and the other half received 368 ppm of nitrogen in the form
NaNO3. The stem weights, in grams, at the end of 140 days were recorded as follows:

Construct a 95% confidence interval for the difference in the mean stem weight between seedlings that receive no nitrogen and those that receive 368 ppm of nitrogen. Assume the populations to be normally distributed with equal variances.

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No Nitrogen Nitrogen 0.32 0.26 0.53 0.43 0.28 0.47 0.37 0.49 0.47 0.52 0.43 0.75 0.36 0.79 0.42 0.86 0.38 0.62 0.43 0.46