An Automobile Parts Store Was Interested in Comparing the Mean

question 131

Essay

An automobile parts store was interested in comparing the mean life length of three brands of automobile brake shoes. The following data represent the life length, measured in thousands of kilometres, of random samples of six sets of brake shoes of each brand: Use the following output from statistical software to determine which of the means differ at the 0.05 level of significance.
Tukey's pairwise comparisons
Family error rate = 0.0500
Individual error rate = 0.0203
Critical value = 3.67
Intervals for (column level mean) - (row level mean)

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Definitions:

Test Statistic

A number derived from sample information, employed in hypothesis testing to decide if the null hypothesis should be discarded.

Sample

A subset chosen from a larger population for the purpose of investigation.

Normal Probability Plot

A graphical technique for assessing whether or not a data set is approximately normally distributed, utilizing a plot of sorted values versus their expected values under normality.

Residuals

Differences between observed and predicted values of data in statistical models, indicating the error in predictions.