A manufacturer of clay roo?ng tiles would like to investigate the effect of clay type on the proportion of tiles that crack in the kiln during ?ring. Two different types of clay are to be considered. One hundred tiles can be placed in the kiln at any one time. Firing temperature varies slightly at different locations in the kiln, and ?ring temperature may also affect cracking. Discuss the design of an experiment to collect information that could be used to decide between the two clay types. How does your proposed design deal with the extraneous factor temperature?
different types: one focusing on low interest rates, one featuring low fees for ?rst-time buyers, and one appealing to people who may want to re?nance their homes. The lender would like to determine which advertisement format is most successful in attracting customers to call for more information. Describe an experiment that would provide the information needed to make this determination. Be sure to consider extraneous factors, such as the day of the week that the advertisement appears in the paper, the section of the paper in which the advertisement appears, or daily ?uctuations in the interest rate. What role does randomization play in your design?