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In: Statistics and Probability

Mean typing speed is 90 wpm, with a standard deviation of 18 wpm. Find the probability...

Mean typing speed is 90 wpm, with a standard deviation of 18 wpm. Find the probability of a randomly selected sample of n = 49 typists has a mean speed of less than 85 wpm. Round your result to 4 decimal places.

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Expert Solution

Solution :

Given that ,

mean =   = 90

standard deviation = = 18

n = 49

=

=  / n = 18 / 49=2.5714

P( <85 ) = P[( - ) / < (85 -90) /2.5714 ]

= P(z <-1.94 )

Using z table  

= 0.0262

probability=0.0262   

probability=   

orchestra answered 2 years ago
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