Comments on: How to find the probability for this event? http://boatdonationsmaryland.com/182/how-to-find-the-probability-for-this-event/ Donate Your Boat and Help a Marine Charity Thu, 31 Dec 2009 12:19:14 +0000 hourly 1 http://wordpress.org/?v=3.0.1 By: Merlyn http://boatdonationsmaryland.com/182/how-to-find-the-probability-for-this-event/comment-page-1/#comment-302 Merlyn Sun, 21 Jun 2009 07:43:54 +0000 http://boatdonationsmaryland.com/182/how-to-find-the-probability-for-this-event/#comment-302 The sum of normal random variables is also a normal random variable. the mean is the sum of the means and the variance is the sum of the variances. this is only true if the variables are independed, which they are in this case. X ~ Normal( ?x = 4200 , ?x² = 9025 ) X ~ Normal( ?x = 4200 , ?x = 95 ) Find P( X > 4250 ) P( ( X - ? ) / ? > ( 4250 - 4200 ) / 95 ) = P( Z > 0.5263158 ) = P( Z < -0.5263158 ) = 0.2993344 The sum of normal random variables is also a normal random variable. the mean is the sum of the means and the variance is the sum of the variances. this is only true if the variables are independed, which they are in this case.

X ~ Normal( ?x = 4200 , ?x² = 9025 )
X ~ Normal( ?x = 4200 , ?x = 95 )

Find P( X > 4250 )
P( ( X – ? ) / ? > ( 4250 – 4200 ) / 95 )
= P( Z > 0.5263158 )
= P( Z < -0.5263158 )
= 0.2993344

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