A standardized visual working memory test has a population mean (μ) of 15 and a standard deviation (σ) of 8. Because the scores are normally distributed, the whole distribution of scores can be converted into a Z distribution. Each raw score in the original distribution has a corresponding Z score in the Z distribution. The Z distribution has symmetrical bell shape with known properties, so it’s possible to mathematically figure out the percentage of scores within any specified area in the distribution. – John’s Z score= (X-M)/SD = (13-15)/8= -0.25 What is the percentage of students that score lower than John?
A standardized visual working memory test has a population mean (μ) of 15 and a standard deviation (σ) of 8.
Because the scores are normally distributed, the whole distribution of scores can be converted into a Z distribution. Each raw score in the original distribution has a corresponding Z score in the Z distribution. The Z distribution has symmetrical bell shape with known properties, so it’s possible to mathematically figure out the percentage of scores within any specified area in the distribution.
– John’s Z score= (X-M)/SD = (13-15)/8= -0.25
What is the percentage of students that score lower than John?