Question

he number of lightening strikes on a square kilometer of open ground in a year has mean 5 and standard deviation 2.1. The National Lightening Detection Network used automatic sensors to watch for lightening in a sample of 16 randomly chosen square kilometers.

What is the probability that the average number of lightening strikes per kilometer per year for 16 randomly chosen square kilometers is 4.8 or more?

Answer #1

Solution :

Given that ,

mean = = 5

standard deviation = = 2.1

n = 16

= 5

= / n = 2.1/ 16 = 0.525

P( >4.8 ) = 1 - P( <4.8 )

= 1 - P[( - ) / < (4.8-5) /0.525 ]

= 1 - P(z <-0.38 )

Using z table

= 1 - 0.3520

= 0.6480

probability= 0.6480

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