# Statistics

posted by .

1. The mean and standard deviation of the grades of a group of students who took an economic exam  were 69 and 7, respectively. The grades have a mound-shaped distribution. According to the Empirical Rule,

b) Approximately what percentage of grades were between 55 and 76?

• Statistics -

a. 68% are mean ± 1 SD.

b. Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions related to the Z scores (from Z = -2 to +1).

## Similar Questions

1. ### college

Suppose that, for a certain exam, a teacher grades on a curve. It is known that the grades follow a normal distribution with a mean of 70 and a standard deviation of 7. There are 45 students in the class. How many students should receive …
2. ### Quantitative methods

the mean and standard deviation of the grades of 500 students who took an maths exam were 69 and 7 respectively. if the grades have a bell shaped distribution, how many of these students received a grade of more than 83 marks?
3. ### Quantitative methods

the mean and standard deviation of the grades of 500 students who took an maths exam were 69 and 7 respectively. if the grades have a bell shaped distribution, how many of these students received a grade of more than 83 marks?
4. ### statistics

If the grades on a police entrance exam are normally distributed with a mean of 100 and a standard deviation of 15, what percentage of students received grades of less than 115?
5. ### statistics

Percentage grades in a large physics class follow a normal distribution with mean 58. It is known that 3% of students receive grades less than 39.2. What is the standard deviation of grades in the class?
6. ### 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 below.) …