The distribution of net typing rate in words per minute (wpm) for experienced typists can be approximated by a normal curve with mean 60 wpm and standard deviation 15 wpm. Suppose that special training is to be made available to the slowest 20% of the typists. What typing speeds would qualify individuals for this training?
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you need to find the z-score that has area below is 0.2000.This z-score is
Now use the formula
z=(x-mu)/sigma
-0.84=(X-60)/15
-0.84*15=X-60
-12.6=X-60
X=-12.6+60= 47.4 or 47 words or lower
Now use the formula
z=(x-mu)/sigma
-0.84=(X-60)/15
-0.84*15=X-60
-12.6=X-60
X=-12.6+60= 47.4 or 47 words or lower
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20% means the area under the standard normal curve in the extreme left tail is 0.2000
The z value which divides the total area under the standard normal curve into two parts viz., 0,2000 and 0.8000 is to ascertained.
The z value is - 0.84 approximately
- 0.84 = X - 60 / 15
- 12.60 = X-60
X = 47.4
Required typing speed is 47.4 wpm
The z value which divides the total area under the standard normal curve into two parts viz., 0,2000 and 0.8000 is to ascertained.
The z value is - 0.84 approximately
- 0.84 = X - 60 / 15
- 12.60 = X-60
X = 47.4
Required typing speed is 47.4 wpm