Does anybody know how to find percentage in a normal curve???
the scholastic assessment test (SAT) is standardized to be normally distributed with a mean of 500 and standard deviation of 100, what percentage of SAT scores falls
a.) between 500 and 600
b.) between 400 and 600
c.) between 500 and 700
d.) between 300 and 700
e.)above 600?
f.) below 300?
Favorite Answer
b=68% because 400 and 600 are each 1 standard deviation from the mean, and d=95% since 300 and 700 are each 2 standard deviations from the mean. The formula to figure out the rest of them is (score-mean)/standard deviation. You can convert the standard deviations to percentages easily since the SD for this problem is 100. If you don’t want to use the formula, you can just plot the rest of them on a normal curve, using the information I’ve given you to figure out the percentages.
z = (Raw score – Mean) / Standard Deviation
a. Area between 500 and 600 = area below 600 – area below 500
z score for 600 = (600 – 500)/100 = 1
That means that 600 is one standard deviation greater than the mean. Since the distribution is normal we can go to the table and read off the fraction of the area beneath the normal curve that is less than or equal to one standard deviation
Area below 600 = 0.841345 (by calculator)
The area below 500 is exactly half the area below the normal curve, because 500 is the mean
Area below 500 = 0.5 (because 500 is the mean)
Therefore the area between 500 and 600 = 0.841345 – 0.5
= 0.341345
= 34% to nearest integer
(b) z score for 400 = -1 and z score for 600 = 1
Area below 400 = 0.158655 (by calculator)
Area below 600 = 0.841345 (by calculator)
Therefore the area between 400 and 600 = 0.68269
= 68% to nearest integer
Make sure you understand why the answer to (b) is exactly double the answer to (a). After that, all the questions are the same.
http://www.caladis.org/compute/?q=%24SATscore&v=SATscore%3Anorm%2C500%2C100&x=off&n=m&h=fd&a=rad