A study sought to demonstrate that soy beans inoculated with nitrogen-fixing bacteria have higher yields and remain healthy without the use of fertilizers. It was conducted under carefully controlled conditions, with all plants having the same soil type and the same amounts of soil, water, light, nutrients and space. There were 8 inoculated plants and 8 un-inoculated plants. Plant yield was measured by pod weight (in grams, g), and the data are in the file NitFix on LMS, in columns headed Ipod and Upod, for inoculated and un-inoculated pod weights, respectively.
a) What kind of hypothesis test should be used to compare the mean yields in the two groups of plants? Justify your choice.
b) Produce the following computer output for the hypothesis test selected in part (a):
i) Analysis that includes all relevant calculations.
ii) A suitable graph of the data.
c) Is it true that, on average, the yield from inoculated soy bean plants exceeds that from un-inoculated soy bean plants? Investigate this question by means of a hypothesis test, using a P-value approach and a significance level of 5%. Refer to your computer output where appropriate.
d) Using descriptive statistics from your computer output in part (b), calculate a 90% confidence interval for the difference in mean yield between inoculated and un-inoculated soybean plants.
e) Provide an interpretation of the confidence interval calculate in part (d)
f) Using descriptive statistics from your computer output in part (b), calculate a 95% confidence interval for the mean yield of inoculated soybean plants.
what is the right way of answering this question?