Exam Grades \( A \) statistics professor is used to having a variance in his class grades of no more than 100 . He feels that his current group of students is different, and so he examines a random sample of midterm grades (listed below). At \( \alpha=0.01 \), can it be concluded that the variance in grades exceeds 100 ? Assume the variable is normally distribujed. \( \begin{array}{ccccccc}68.7 & 49.1 & 75.8 & 52.8 & 92.3 & 96.7 & 89.4 \\ 65.2 & 69.5 & 72.8 & 67.5\end{array} \) Send data to Excel.

A variable is normally distributed with mean 18 and standard deviation 9 . Use your graphing calculator to find each of the following areas. Write your answers in decimal form. Round to the nearest thousandth as needed. a) Find the area to the left of 17.

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A variable \( x \) is normally distributed with mean 21 and standard deviation 5. a) Determine the \( z \)-score for \( x=27 \). b) Determine the \( z \)-score for \( x=15 \). c) What value of \( x \) has a \( z \)-score of 1.8 ? \( x=x= \) d) What value of \( x \) has a \( z \)-score of -0.6 ? e) What value of \( x \) has a \( z \)-score of 0 ? \( x= \)

A set of exam scores is normally distributed with a mean \( =74 \) and standard deviation \( =8 \). \( 95 \% \) of the data values lie between 58 \( \% \) of the exam scores are between 66 and 74 . \( \% \) of the exam scores are between 74 and 90 . \( \% \) of the exam scores are between 82 and 90 . \% oxam scores are greater than or equal to 66 .

The weights for newborn babies is approximately normally distributed with a mean of 6 pounds and standard deviation of 1.5 pounds. Consider a group of 1100 newborn babies: 1. How many would you expect to weigh between 3 and 8 pounds? 2. How many would you expect to weigh less than 7 pounds? 3. How many would you expect to weigh more than 6 pounds? 4. How many would you expect to weigh between 6 and 9 pounds?