The mean number of words per minute (WPM) read by sixth graders is 81 with a standard deviation of 17 WPM. If 130 sixth graders are randomly selected, what is the probability that the sample mean would be greater than 77.21 WPM? Round your answer to four decimal places.

Answer:The probability that the sample mean would be greater than 77.21 WPM = 0.9945Step-by-step explanation:Mean number of Words per Minute  = u  = 81Standard Deviation = s = 17sample size = n = 130Target value = x = 77.21we can find the probability by converting x to z-score.The formula for z-score = [tex]\frac{x-u}{\frac{s}{\sqrt{n} } }[/tex]using given values, z-score =  [tex]\frac{77.21-81}{\frac{17}{\sqrt{130} } }[/tex]=> -2.54using the z table, we can find the find the probability of -2.54, that is 0.9945.Therefore, the probability that the sample mean would be greater than 77.21 WPM = 0.9945