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Many residents in a small town have developed a bacterial infection. Two students hypothesize that the bacteria are coming from the town’s drinking water. They look for the bacteria in water samples from the lake that supplies 80 percent of the town’s drinking water. When they find no bacteria, the students conclude that the town’s residents are not getting the bacteria from their drinking water. Which is a source of error in the students’ experimental design?



Answer :

The students only tested the drinking water supplied by the lake. This 80% may not contain the bacterial infection, but the other 20% from unknown sources(which they didn't account for in their conclusion) may.
akposevictor

OPTIONS:

a. Water from the late was not tested for other possible pathogens b. Residents of other nearby towns were not tested for the bacteria c. The residents' genetic predisposition for getting ill was not determined d. Other sources of drinking water were not tested for bacteria

Answer:

d. Other sources of drinking water were not tested for bacteria

Explanation:

The source of error in the experimental design of the students stems from the failure to collect samples from other sources of the town's drinking water. The samples collected and tested were simply unrepresentative of the drinking water supply of the town, as the samples collected only represented water from the lake, which is 80% of the town's supplies of drinking water.

To arrive at a good conclusion, samples collected should represent adequately, all sources of drinking water of the town, rather than just representing supply from mainly the lake, which accounts for 80%.

It could be that the source of bacterial infection might emanate from other sources of drinking water that was not represented in the samples collected for testing.

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