In order to estimate the mean amount of time computer users spend on the interne

Question

In order to estimate the mean amount of time computer users spend on the internet each month, how many computer users must be surveyed in order to be 90% confident that your sample mean is within10 minutes of the population mean? Assume that the standard deviation of the population of monthly time spent on the internet is 225 min. What is a major obstacle to getting a good estimate of the population mean? Use technology to find the estimated minimum required sample size.

The minimum sample size required is______computer users. (Round up to the nearest whole number.)

What is a major obstacle to getting a good estimate of the population mean?

A.There may not be 1,370 computer users to survey.

B.It is difficult to precisely measure the amount of time spent on the internet, invalidating some data values.

C.The data does not provide information on what the computer users did while on the internet.

D.There are no obstacles to getting a good esitmate of the population mean.

_________________________________________________________________________________________________________________

(2nd problem needing help)

If we find that there is a linear correlation between the concentration of carbon dioxide in our atmosphere and the global temperature, does that indicate that changes in the concentration of carbon dioxide cause changes in the globaltemperature?

Choose the correct answer below.

A. Yes. The presence of a linear correlation between two variables implies that one of the variables is the cause of the other variable.

B. No. The presence of a linear correlation between two variables does not imply that one of the variables is the cause of the other variable.

Explanation / Answer

In order to estimate the mean amount of time computer users spend on the internet each month, how many computer users must be surveyed in order to be 90% confident that your sample mean is within10 minutes of the population mean? Assume that the standard deviation of the population of monthly time spent on the internet is 225 min. What is a major obstacle to getting a good estimate of the population mean? Use technology to find the estimated minimum required sample size.
The minimum sample size required is______computer users. (Round up to the nearest whole number.)

Note that      
      
n = z(alpha/2)^2 s^2 / E^2      
      
where      
      
alpha/2 = (1 - confidence level)/2 =    0.05  
      
Using a table/technology,      
      
z(alpha/2) =    1.644853627  
      
Also,      
      
s = sample standard deviation =    225  
E = margin of error =    10  
      
Thus,      
      
n =    1369.681374  
      
Rounding up,      
      
n =    1370   [ANSWER]

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What is a major obstacle to getting a good estimate of the population mean?

B.It is difficult to precisely measure the amount of time spent on the internet, invalidating some data values. [ANSWER]

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If we find that there is a linear correlation between the concentration of carbon dioxide in our atmosphere and the global temperature, does that indicate that changes in the concentration of carbon dioxide cause changes in the globaltemperature?

OPTION B: B. No. The presence of a linear correlation between two variables does not imply that one of the variables is the cause of the other variable. [ANSWER]

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