A laundry detergent manufacturer wished to test a new product prior to market release. One area of concern was the relationship between the height of the detergent suds in a washing machine as a function of the amount of detergent added and the degree of agitation in the wash cycle. For a standard size washing machine tub filled to the full level, random assignments of different agitation levels (measured in minutes) and amounts of detergent were made and tested on the washing machine. The data are shown in the accompanying table.
a. Plot the data and suggest a model.
b. Does the assumption of normality appear to hold?
c. Fit an appropriate model.
d. Use residual plots to detect possible violations of the assumptions.

  • CreatedNovember 21, 2015
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