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S2: why can't I do this?

This is the question:

A web server is visited on weekdays at a rate of 7 visits per minute. In a random 2 minute period on a saturday, the web server is visited 20 times. Use a suitable approximation to test to 10% level of significance whether or not visits is greater on a saturday.

In the mark scheme:

They've multiplied 7 by 2 because they've adopted the time interval as two minutes. So that they have '20' and '14' for a two minute interval.

Why can't I keep '7' as it it, and halve 20 to get it to 10, so that both the rate of visits, '10' and the mean, '7' are for a one minute interval instead of two minutes as they've done it?
because if you halve the evidence time period then you are assuming there are ten visits in each minute but there may have been 6 in the first minute and 14 in the second. Since the poisson distribution says there or on average 7 visits per minute, you can scale this up or down as you like.
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W.H.T
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Original post by connoryoung
because if you halve the evidence time period then you are assuming there are ten visits in each minute but there may have been 6 in the first minute and 14 in the second. Since the poisson distribution says there or on average 7 visits per minute, you can scale this up or down as you like.


Thanks, I understand this better now

:tongue: I think I phrased my question quite badly, but I'm glad you understod it

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