# elementary statistics

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 0.05 alpha level can it be conculded that the variance in the grades differs from 100? Write a 90% confidence level of the variance using the information given
92.3 89.4 76.9 65.2. 49.1. 96 7. 69.5. 72.8. 77.5 52.8. 8.85. 79.2. 72.9. 68.7. 75.8

1. 👍
2. 👎
3. 👁
1. There are different ways you can do this kind of problem, but the formula below might be one of the easier ways:

s/[1 + (1.645/âˆš2n)]
..to..
s/[1 - (1.645/âˆš2n)]

...where s = standard deviation, 1.645 represents the 90% confidence interval using a z-table, and n = sample size.

You will need to calculate standard deviation from the data given, then substitute the standard deviation and sample size into the formula.

After you finish the above calculations, square the standard deviation values to find the variance values.

I hope this will help get you started.

1. 👍
2. 👎

## Similar Questions

1. ### Statistics - M/C

14. The marks on a statistics test are normally distributed with a mean of 62 and a variance of 225. If the instructor wishes to assign Bâ€™s or higher to the top 30% of the students in the class, what mark is required to get a B

2. ### math

Professor Ivy has given the following weights to her grades: Weight of Area Homework 5% Projects 20% Quiz 15% Exams 60% Your friend has the following averages: Homework: 99 Projects: 85 Quizzes: 30 Exams: 70 Calculate his grade

3. ### statistics

A history class has 75 members. If there is a 12% absentee rate per class meeting, find the mean, variance, and atandard deviation of the number of students who will be absent from each class

4. ### Math

In a large section of a statistics class, the points for the final exam are normally distributed, with a mean of 72 and a standard deviation of 9. Grades are to be assigned according to the following rule: The top 10% receive A's.

1. ### Statistics

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

2. ### statistics

In your sample of 23 art students and 30 economics students, the mean amount that a group of economics students like statistics is 26, while the mean amount that a group of art students like statistics is 15. The variance in the

3. ### Statistics

80. Florida State University has 14 statistics classes scheduled for its Summer 2013 term. One class has space available for 30 students, eight classes have space for 60 students, one class has space for 70 students, and four

4. ### Statistics

Which Professor? Suppose Professor Alpha and Professor Omega each teach Introductory Biology. You need to Decide which professor to take the class from and have just completed your introductory statistics course. Records obtained

1. ### Statistic

professor has found that the grades on a Statistics Exam are normally distributed with mean 72 and a standard deviation of 12. If only the best 15 % of the grades in the class will get an A, what grade must a student get in order

2. ### Math

In a large section of a statistics class, the points for the final exam are normally distributed, with a mean of 72 and a standard deviation of 9. Grades are to be assigned according to the following rule: The top 10% receive A's.

3. ### statistics

An instructor in a large lecture class found at the end of the semester that total points scored by students in his class was approximately Normal with mean 530 and standard deviation 80. If 10% of the class are to receive A's (he

4. ### Statistics

Hi, My professor gave us the formulas for sample variance and population variance, as well as the shortcut formulas for each. However, he said that on some of the problems, we will HAVE to use the long formula, which for