Question: Chemical properties of whole wheat breads. Whole wheat breads contain a high amount of phytic acid, which tends to lower the absorption of nutrient minerals. The Journal of Agricultural and Food Chemistry (January 2005) published the results of a study to determine if sourdough can increase the solubility of whole wheat bread. Four types of bread were prepared from whole meal flour: (1) yeast added, (2) sourdough added, (3) no yeast or sourdough added (control), and (4) lactic acid added. Data were collected on the soluble magnesium level (percent of total magnesium) during fermentation for dough samples of each bread type, and analyzed using a one-way ANOVA. The four mean soluble magnesium levels were compared in pairwise fashion using Bonferroni's method.

(a) How many pairwise comparisons are made in the Bonferroni analysis?

(b) The experimentwise error rate for the analysis was. 05. Interpret this value.

(c) Based on the experimentwise error rate, part b, what comparisonwise error rate is used with each comparison made in the Bonferroni analysis?

(d) The results of the Bonferroni analysis are summarized below. Which treatment(s) yielded the significantly highest mean soluble magnesium level? The lowest?

Mean:                 7%             12.5%             22%               27.5%

Bread type:       Control           Yeast           Lactate         Sourdough