Question

eduardos mother just bought a new vacuum cleaner that she loves. eduardo wants to know if it really cleans better than the old one. he gets a few identical carpet samples and works an equal amount of sand and dirt into each one. then he gets a panel of ten people to rate how well each vacuum cleans. which of the following experimental setups will be the most objective and have the least bias? a. the panelists watch eduardo use each vacuum to clean a carpet sample, then they rate how clean each sample is. b. each panelist cleans one carpet sample with each vacuum, then rates how clean each sample is. c. eduardo leaves 1/3 of the samples dirty. he divides the other samples into two groups. he cleans each group with a different vacuum. he puts the samples in a random order, then asks the panelists to rate how clean each sample is. d. eduardo leaves 1/3 of the samples dirty. he divides the other samples into two groups. he cleans each group with a different vacuum, then he asks the panelists to rate how clean each group is.

Explanation:

To minimize bias, the samples should be presented randomly and rated individually. Option C does this. In Option A, watching Eduardo clean may introduce bias. In Option B, panelists cleaning themselves can lead to inconsistent results and bias. Option D rates groups instead of individual samples, which is less precise.

Answer:

C. Eduardo leaves 1/3 of the samples dirty. He divides the other samples into two groups. He cleans each group with a different vacuum. He puts the samples in a random order, then asks the panelists to rate how clean each sample is.