For the majority of maths tests taken at a school, it is shown that the test score is approximaly normally distributed with a mean of 100 and a standard deviation of 15. i. If the random variable ?, is the math test score, state the value/s of its parameter/s. ii. Find the probability that a random score lies between 90 and 115. iii. Find the probability that the average of nine random scores lies between 90 and 115.

A professor of statistics noticed that the marks in his course are normally distributed. He also noticed that his morning classes average 73% with a standard deviation of 12% on their final exams. His afternoon classes average 79% with a standard deviation of 11%. A. What is the probability that a randomly selected student in the morning class has a higher final exam mark than a randomly selected student from an afternoon class? Probability =  B. What is the probability that the mean mark of four randomly selected students from a morning class is greater than the average mark of four randomly selected students from an afternoon class? Probability =

Refer to the accompanying table, which describes results from groups of 8 births from 8 different sets of parents. The random variable x represents the number of girls among 8 children. Find the mean and standard deviation for the number of girls in 8 births. Click the icon to view the data table. The mean is u= girl(s). (Round to one decimal place as needed.) The standard deviation is o = e# girl(s). (Round to one decimal place as needed.) Table of numbers of girls and probabilities Number of Girls x 0 1 2 3 4 5 6 7 8 átv P(x) 0.004 0.034 0.117 0.218 0.278 0.217 0.102 0.027 0.003 D - X NiZ Next

Refer to the accompanying table, which describes results from groups of 8 births from 8 different sets of parents. The random variable x represents the number of girls among 8 children. Find the mean and standard deviation for the number of girls in 8 births. Click the icon to view the data table. The mean is u = girl(s). (Round to one decimal place as needed.) The standard deviation is o = girl(s). (Round to one decimal place as needed.)