The reading speed of second grade students is approximately normal, with a mean of 88 words per minute (wpm) and a standard deviation of 12 wpm. a) what is the probability a randomly selected student will read more than 95 words per minute? b) what is the probability that a random sample of 12 second grade students results in a mean reading rate of more than 95 words per minute? c) what is the probability that a random sample of 24 second grade students results in a mean reading rate of more than 95 words per minute? d) what effect does increasing the sample size have on the probability? provide an explanation for this result.

"The reading speed of second grade students is approximately normal, with a mean of 88 words per minute (wpm) and a standard deviation of 12 wpm. a) What is the probability a randomly selected student will read more than 95 words per minute?"
                                                                95-88               7
Calculate the z-score for 95 wpm:  z = =
                                                                     12               12

This fraction is approx. equal to 0.583.

Look in the body of a table of positive z scores for this 0.583.  The table will give you a decimal fraction that represents the area to the LEFT of z=0.583.
Subtract that result from 1.000 to obtain the probability that a student's typing skills will be greater than 95 wpm.  If you have a calculator with the normal cumulative density function (normalcdf) built in, find the area under the normal curve to the left of 0.583 and then subtract this result from 1.000.

My calculator result was 1.000-0.720 = 0.280.

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