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Assuming equal numbers of observations in each of the two samples, find the sample sizes needed...

Assuming equal numbers of observations in each of the two samples, find the sample sizes needed to estimate the difference in population means correct to within 2.5 with probability 0.90. From prior experience, we know that the standard deviation of population 1 is 18 and the standard deviation of population 2 is 16.

Group of answer choices

We need a sample of 251 observations from population 1 and a sample of 251 observations from population 2.

We need a sample of 15 observations from population 1 and a sample of 15 observations from population 2.

We need a sample of 30 observations from population 1 and a sample of 30 observations from population 2.

We need a sample of 252 observations from population 1 and a sample of 252 observations from population 2.

Math   Statistics-And-Probability   
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Answer #1

Given that, margin of error (E) = 2.5

population standard deviation 1 = 18

population standard deviation 2 = 16

A 90% confidence level has significance level of 0.10 and critical value is,

We want to find, the sample size (n1 = n2 = n),

Therefore, we need a sample of 252 observations from population 1 and a sample of 252 observations from population 2.

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