Answer:
D. The 95% confidence interval ranges from 42.78 to 47.22 hours.
Step-by-step explanation:
In a sample of 50 households, the mean number of hours spent on social networking sites during the month of January was 45 hours. In a much larger study, the standard deviation was determined to be 8 hours.
Here,
n = sample size = 50,
μ = mean = 45,
σ = standard deviation = 8,
We know that, confidence interval will be,
![=\mu\ \pm\ z\dfrac{\sigma }{\sqrt{n}}](https://tex.z-dn.net/?f=%3D%5Cmu%5C%20%5Cpm%5C%20z%5Cdfrac%7B%5Csigma%20%7D%7B%5Csqrt%7Bn%7D%7D)
For a confidence interval of 95%, we use z = 1.96, putting the values
![=45\ \pm\ 1.96\dfrac{8}{\sqrt{50}}](https://tex.z-dn.net/?f=%3D45%5C%20%5Cpm%5C%201.96%5Cdfrac%7B8%7D%7B%5Csqrt%7B50%7D%7D)
![=42.78,47.22](https://tex.z-dn.net/?f=%3D42.78%2C47.22)