# Question: A large laboratory has four types of devices used to

A large laboratory has four types of devices used to determine the pH of soil samples. The laboratory wants to determine whether there are differences in the average readings given by these devices. The lab uses 24 soil samples having known pH in the study and randomly assigns six of the samples to each device. The soil samples are tested, and the response recorded for each sample is the difference between the pH reading of the device and the known pH of the soil. These values, along with summary statistics, are given in the following table.

a. Based on your intuition, is there evidence to indicate any difference among the mean differences in pH readings for the four devices?

b. Run an analysis of variance to confirm or reject your conclusion in part (a). Use α = .05.

c. Compute the p-value of the F test in part (b).

d. What conditions must be satisfied for your analysis in parts (b) and (c) to be valid?

e. Suppose the 24 soil samples have widely different pH values. What problems may occur by simply randomly assigning the soil samples to the different devices?

a. Based on your intuition, is there evidence to indicate any difference among the mean differences in pH readings for the four devices?

b. Run an analysis of variance to confirm or reject your conclusion in part (a). Use α = .05.

c. Compute the p-value of the F test in part (b).

d. What conditions must be satisfied for your analysis in parts (b) and (c) to be valid?

e. Suppose the 24 soil samples have widely different pH values. What problems may occur by simply randomly assigning the soil samples to the different devices?

## Relevant Questions

It is conjectured that when fields are overgrazed by cattle there will be a substantial reduction in the available grass during the subsequent grazing season due to the compaction of the soil. A horticulturist at the state ...Researchers conducted an experiment to compare the effectiveness of four new weight- reducing agents to that of an existing agent. The researchers randomly divided a random sample of 50 males into five equal groups with ...Refer to Exercise 8.28. a. Compare the mean yields of herbicide 1 and herbicide 2 to the control treatment. Use a = .05. b. Should the procedure you used in part ( a) be a one- sided or a two- sided procedure? c. Interpret ...Refer to Exercise 8.23. In exercise a. Use a nonparametric procedure to compare the mean reliability of the seven plants. b. Even though the necessary conditions are not satisfied, use the Tukey’s W proce-dure to group the ...For each of the following values for p^ and n, compute a 99% confidence interval for the population proportion p using both the standard large- sample procedure and the WAC adjusted procedure. Comment on whether the WAC ...Post your question