Mariano determined that the more he practiced piano the less mistakes he would make. he found that for each hour ne
practiced each week he could decrease his mistakes by 30%. mariano computed a best-fit equation of y=-0.3x + 17
where y is the total mistakes and x is the number of hours practiced. use mariano's equation to estimate the number of
mistakes per page made by a student who has practiced for 21 hours. round to the nearest tenth if necessary.

answer: huh

step-by-step explanation:

step-by-step explanation:

what is the your question?

irst, find the z score of a score of 80. this is given by the formula z = (x-u)/o, where x is the score, u is the mean, and o is the standard deviation. this gives

z = (80-78)/12 = 1/6 = .1667

now, find what percentile a z score of 1/6 correlates to in the normal distribution.

a z score of 1/6 = .1667 is equivalent to the 56.36th percentile of the distribution. so the probability a score is over this is 1-.5636 = .4364

the mean of a sample mean is equal to the original mean. however, the standard deviation of a sample mean is equal to the original standard deviation divided by the square root of n (sample size). so the new standard deviation is 12/sqrt(16) = 3.

the new z score is 80-78/3 = 2/3 = .667. this is equivalent to the 74.86th percentile. so the probability that the mean will be greater than this score is 1-.7486 = .2514.