Question

Suppose that the distribution of typing speed in words per minute (wpm) for experienced typists using a new type of split keyboard can be approximated by a normal curve with mean 64 wpm and standard deviation 15 wpm. b. What is the probability that a randomly selected typists typing speeds is between 45 and 90 wpm? Round your answer to four decmial places. Would you be surprised to find a typist in tis pop. to excced 105 wpm? Suppose two typists re indepentdnly selected. What is the proablity that their speed will exceed 75 wpm? Round 4 decimals. What is the proablity that a typists speed is less than 60 wpm? Round to one decimal

Answer 1

X: typing speed in words per minute

X ~ N (64,15)

a).the probability that a randomly selected typists typing speeds is between 45 and 90 wpm is:-

[ in any blank cell of excel type =NORMSDIST(1.7333) ]

[ in any blank cell of excel type =NORMSDIST(-1.2667) ]

b)the probability that  a typist in this population to exceed 105 wpm is:-

[ in any blank cell of excel type =NORMSDIST(2.7333) ]

YES, i will be surprised if a typist in this population to exceed 105 wpm , because the probability is 0.0031 < 0.05 .

c).sample size (n) =2

the sample mean will follow normal distribution with :-

the probability that their speed will exceed 75 wpm is:-

[ in any blank cell of excel type =NORMSDIST(1.7333) ]

d).the probability that a typists speed is less than 60 wpm is:-

[  in any blank cell of excel type =NORMSDIST(-0.2667) ]

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