posted by Tommy .
The distribution of scores on the SAT is approx. normal with mu= 500 and std dev=100.
a)what proportion of the population have SAT scores above 650?
b)what proportion of of the population have SAT scores below 540?
c)what is the minimum SAT score needed to be in the highest 20% of the population?
d)what SATE scores separates the top 60% from the rest of the distribution?
Use the Z score formula:
Z = (X - ƒÊ)/SD
After finding the appropriate Z scores in a table in the back of your statistics text called something like "areas under the normal distribution," insert that Z value into the formula to find the value of your score.
Some problems need you to determine the Z score before consulting this table to get a proprotion.
I hope this helps. Thanks for asking.