Imagine that you are an expert in Website Analytics, and you have been hired to manage a company's websites. A successful website is one where visitors come and spend time on the site. More time spent on the site is desirable because you can then convince advertisers to pay you to place their ads on your sites. You have been asked to analyze performance of the following websites:

WGG.com - "Watching Grass Grow", a website showing real-time video of a field of grass growing on the lawn. Some data collection analysis of WGG visitors showed that out of 100 unique visitors, the average duration was equal to 2 minutes, with a standard deviation equal to 20 minutes.

1. With 99% confidence, calculate an interval that estimates the true duration of time a visitor would spend on the WGG site.

Answer: we know SD = 20 min, mean = 2 min, sample(n) = 100 people, 99% confidence with z-score value = 2.575

CI = 2 ± 2.575 * (20/) = 2 ± 5.15, CI = (-3.15, 7.15)

Is it possible that the number in the confidence interval is negative? Also, the time(min) in negative doesn't make any sense, we can't say someone spends -3.15 minutes on WGG site, so can I retain the answer like this or not?

pur-new-sol

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