Define a z-score, and explain how it is calculated in the following example: Abby had a score of 75 on a test with a mean of 70 and a standard deviation of 5 . What is her z-score?
What will be an ideal response?
Answer will include that a z-score is a number (a standard score) that tells how many standard deviations above or below the mean score is. To convert an original score to a z-score, we subtract the mean from the score. The resulting number is then divided by the standard deviation for the group of scores. To illustrate, Abby had a score of 75 on the test with a mean of 70 and a standard deviation of 5 . Therefore, 75 minus 70 equals 5, which is divided by the standard deviation of 5 and equals 1 . So, Abby's z-score is +1.0, which means her test score of 75 is one standard deviation above the mean.
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After collecting data, a researcher determines that states that have instituted a death penalty have shown a decrease in murders. Assuming that the data are accurate, what can you safely conclude?
a. The relationship has been brought about by another variable. b. States that do not have a death penalty should institute one as a deterrent to violent crime. c. There are fewer murders in states that have a death penalty. d. It is likely that violent criminals have moved to states that do not yet have a death penalty.
Even though the amount of improvement declines with age, older adults can improve their memories with training and practice
Indicate whether the statement is true or false.