Question

Two different machines, A and B, used for torsion tests of steel wire were tested on 12 pairs of different types of wire, with one member of each pair tested on each machine.

The results (break angle measurements) were as follows:

Machine A: 32, 35, 38, 28, 40, 42, 36, 29, 33, 37, 22, 42

Machine B: 30, 34, 39, 26, 37, 42, 35, 30, 30, 32, 20, 41

[a] Construct a side-by-side boxplot to display the two data sets and comment on interesting features.                                                                                                                                                                  [4 pt]

[b] Construct a QQ-plot (with a qqline) for each data set.                                                                 [3 pt]

How would you describe your Q-Q plot?

[c] Perform a Shapiro-Wilks normality test on each data set. What are the results regarding the data sets?                                                                                                                                                                        [3 pt]

[d] Based on your results [a] through [c], can you conduct a two-sample t-test for the data sets? Explain your response.                                                                                                             

Answer:           Yes                  No                   E Circle one                                                              [1 pt]

Explanation:                                                                                                                                       [3 pt]

[e] Is there evidence at the 5% significance level to suggest that machines A and B give different mean readings?

Write the null and alternative hypotheses test symbolically and verbally.                                        [8 pt]

Use R to get analysis results. State what the results tell you about the data.                                     [8 pt]

[f] Is there evidence at the 5% significance level to suggest that machine B gives a lower average reading than machine A?

Write the null and alternative hypotheses test symbolically and verbally.                                        [8 pt]

Use R to get analysis results. State what the results tell you about the data.                                     [8 pt]

[g] Your R codes or Excel commands for parts [a], [b], [c], [e], and [f] are required for credit.      [10 pt]

Copy and paste them here or paste them onto a blank MS Word document.

Answer 1