statistics
posted by StudentD .
In a psychology class of 100 students, test scores are normally distributed with a mean of 80 and a standard deviation of 5. Approximately what percentage of students have scores between 70 and 90?
A. 68%
B. 80%
C. 95%
D. 99%

You haven't memorized the proportion within 2 standard deviations from the mean?
Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score. 
12

I Do not know
Respond to this Question
Similar Questions

statistics
Using the 689599.7rule. Assume that a set of test scores is normally distributed with a mean of 100 and a standard deviation of 20. Use the 689599.7 rule to find the following quantities: a. percentage of scores less than 100 b. … 
statistics
Assume that a set of test scores is normally distributed with a mean of 100 and a standard deviation of 20. Use the 689599.7 rule to find the following quantities: Suggest you make a drawing and label firstâ€¦ a.Percentage of scores … 
statistics
Suppose you administered an anxiety test to a large sample of people and obtained normally distributed scores with a mean of 45 and standard deviation of 4 There are 200 students in a sample. How many of these students will have scores … 
Statistics
Suppose you administered an anxiety test to a large sample of people and obtained normally distributed scores with a mean of 45 and standard deviation of 4. There are 200 students in a sample. How many of these students will have scores … 
Statistics
18. The Intelligence Quotient (IQ) test scores are normally distributed with a mean of 100 and a standard deviation of 15. Given a class with 25 students, what is the probability that the class' average IQ score is between 85 and 115? 
Statistics
5. Scores on a recent national statistics exam were normally distributed with a mean of 80 and a standard deviation of 6. a. What is the probability that a randomly selected exam will have a score of at least 71? 
Mathstatistics
Assume that a set of test scores is normally distributed with a mean of 100 and a standard deviation of 20. Use the 689599.7 rule to find the following quantiles: a.percentage of scores less than 100 b. relative frequency of scores … 
statistics
The scores for standardized test are normally distributed with a mean of 300 and standard deviation of 39. If the test is given to 700 students, how many are expected to have scores between 300 and 378. 
math
When Mrs. Myles gave a test, the scores were normally distributed with a mean of 72 and a standard deviation of 8. This means that 95% of her students scored between which two scores? 
Algebra
I do not understand this homework at all. Any help or elaboration would be greatly appreciated. Thanks. 100 juniors at Southwest High took the SAT test. The scores were distributed normally with a mean of 22 and a standard deviation …