Final answer:
Replacing a music file with a smaller version will decrease the mean size of the files. The standard deviation will also likely change, potentially decreasing if the file replaced was an outlier.
Step-by-step explanation:
When replacing a music file that takes up 7.5 megabytes with another version that only takes up 4 megabytes, the mean size of the files will decrease. This is because the mean, or average, is calculated by summing all the file sizes and dividing by the number of files. If one of the file sizes becomes smaller, the total sum decreases, thus the mean decreases as well.
The standard deviation, which measures the spread of a set of values, would also likely change. If the original 7.5 megabyte file was significantly different from the average, replacing it with a 4 megabyte file that is closer to the mean would reduce the spread of the values, thus decreasing the standard deviation. However, without additional data about the other file sizes in the set, it is not possible to determine exactly how the standard deviation will be affected.