Final answer:
About 34% of the scores lie between the mean and -1 standard deviation of a normal distribution with a mean of 100 and a standard deviation of 15.
Step-by-step explanation:
The student asked about the percentage of scores that lies between the mean and -1 standard deviation in a normal distribution.
In any normal distribution, approximately 68% of the data fall within one standard deviation of the mean.
This percentage is evenly distributed so that 34% fall between the mean and one standard deviation above, and the same percentage falls between the mean and one standard deviation below.
For a normal distribution with a mean of 100 and a standard deviation of 15, one standard deviation below the mean is 100 - 15, which equals 85. The percentage of scores that lies between the mean (100) and -1 standard deviation (85) is therefore approximately 34%.