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Math·Algebra·Linear equations in one variable
easy
In a study of high-precision manufacturing, a sample of 1,200 microprocessors produced by Machine A had a mean lifespan of 18,400 hours with a standard deviation of 350 hours. A sample of 1,200 microprocessors produced by Machine B had a mean lifespan of 18,400 hours with a standard deviation of 720 hours. Which of the following statements must be true?
A
The mean lifespan of the microprocessors produced by Machine A is greater than the mean lifespan of the microprocessors produced by Machine B, and the lifespans for Machine A are more spread out than the lifespans for Machine B.
B
The mean lifespan of the microprocessors produced by Machine A is equal to the mean lifespan of the microprocessors produced by Machine B, and the lifespans for Machine A are less spread out than the lifespans for Machine B.
C
The mean lifespan of the microprocessors produced by Machine A is less than the mean lifespan of the microprocessors produced by Machine B, and the lifespans for Machine A are more spread out than the lifespans for Machine B.
D
The mean lifespan of the microprocessors produced by Machine A is equal to the mean lifespan of the microprocessors produced by Machine B, and the lifespans for Machine A are more spread out than the lifespans for Machine B.