Normal distribution central limit Theorum

Statistics
Tutor: None Selected Time limit: 1 Day

The average number of hours that a kid spends per day working at  a computer 3.5 hours. This distribution is normally distributed with the STDV of 0.9 hours. What percentage of kids spend more than 3.8 hours per day working at a computer? 

Mar 14th, 2015

To solve this, one must read up on Gaussian Normal Distribution, e.g.:

http://en.wikipedia.org/wiki/Error_function

1.0-0.5*erfc((3.5-3.8)/(sqrt(2)*0.9)) = 0.369... = 36.9%

Sanity check: Average is 3.5h, so 50% of kids spend less than 3.5h, 50% spend more (with Gaussian distribution mean and median are the same). That means that more than 50% of kids will spend LESS than 3.8h, and less than 50% of kids will spend MORE than 3.8h.

More details:

The term A=0.5*erfc() is the cumulative probability yp to that point (from -infinity). Since we want to know the probability from the point to +infinity, we must take 1-A.

Mar 14th, 2015

Studypool's Notebank makes it easy to buy and sell old notes, study guides, reviews, etc.
Click to visit
The Notebank
...
Mar 14th, 2015
...
Mar 14th, 2015
May 25th, 2017
check_circle
Mark as Final Answer
check_circle
Unmark as Final Answer
check_circle
Final Answer

Secure Information

Content will be erased after question is completed.

check_circle
Final Answer