posted by erica .
a mean score on a standardized test is 50 with a standard deviation of 10. What are the following:
1. what scores fall between -1 and +1 standard deviation?
2. what percent of all scores fall between -1 and +1 standard deviation?
3. what score falls at +2 standard deviations?
4. What percentage of scores falls between +1 and +2 standard deviations?
Z score is your score in terms of standard deviations.
Z = (score-mean)/SD
For the percentages, 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. Multiply by 100 for the percentage.