Answer:
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Step-by-step explanation:
Answer:
An appropriate method is to generate a simple random sample of all single-family homes in the city or a stratified random sample by taking a simple random sample from each of the ten district neighborhoods.
Step-by-step explanation:
Since, the city is very large and it is divided into ten districts. So, collecting sample from one district or any particular are did not give the correct estimate of whole city. So, the appropriate method to collect sample is taking the sample randomly from each district and this type of sampling method is called Stratified Sampling.
1/5(x-y) = 1
x+y = 9
x-y = 5 (x5)
x+y = 9
First you want to create both equations so at least one of the variables (x or y) are the same in both equations, so that is why I multiplied the top one by 5, you multiply the whole equation (both sides)
2x = 14
x = 7
Then you either Plus or minus one from the other, I plused the top one onto the bottom one, then solved for x
7 + y = 9
y = 2
Then put x back into one of the first two equations to get Y
Answer:
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Answer:
Step-by-step explanation:
We want to determine a 95% confidence interval for the population mean.
Number of sample, n = 56
Mean, u = 645 hours
Standard deviation, s = 31 hours
For a confidence level of 95%, the corresponding z value is 1.96.
We will apply the formula
Confidence interval
= mean ± z ×standard deviation/√n
It becomes
645 ± 1.96 × 31/√56
= 645 ± 1.96 × 4.142
= 645 ± 8.12
The lower end of the confidence interval is 645 - 8.12 =636.88
The upper end of the confidence interval is 645 + 8.12 =653.12
Therefore, with 95% confidence interval for the population mean life of fluorescent light bulbs is between 636.88 hours and 653.12 hours
