Answer:
Sally's experiment seems to have been well-designed, as she used two identical engines of the same type, filled one with Brand A oil and the other with Brand B oil, and kept the engines running at the same RPM until they quit running. However, there are a few potential issues with the experiment that could affect the validity of her conclusion.
Firstly, the sample size is very small, as Sally only tested two engines. This means that there is a greater possibility that the results could be due to chance or other factors. It would be more valid to test a larger sample size, such as ten engines filled with each brand of oil.
Secondly, there may have been other factors that affected the engines' survival time besides the type of oil used. For example, the engines may have been slightly different in quality, or they may have been exposed to slightly different environmental conditions, such as temperature or humidity levels.
Therefore, while Sally's conclusion that Brand B oil caused the engine to survive longer may be valid, it should be taken with caution due to the small sample size and potential confounding factors. Further testing with a larger sample size and more control over environmental factors would be needed to confirm the conclusion.