Your answer will be A, 20 hours to take the crew to complete a building with 200 windows
Answer:
Step-by-step explanation:
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The answer is 5.5
The standard deviation (sd or σ) of the sample mean difference is:
sd = √(sd₁²/n₁ + sd₂²/n₂)
For the population A:
sd₁ = 17.6
n₁ = 25
For the population B:
sd₂ = 21.2
n₂ = 30
Hence:
sd = √(sd₁²/n₁ + sd₂²/n₂)
= √(17.6²/20 + 21.2²/30)
= √(309.76/20 + 449.44/30)
= √(15.49 + 14.98)
= √(30.47)
= 5.5
845,000 because 5,00 would be the nearest and 1 rounds down so..