Answer:
(a) Nominal data
(b) Calculating the mean is wrong
Explanation:
Given
 Basketball
 Basketball
 Baseball
 Baseball
 Football
 Football
 Others
 Others
Solving (a): The level of measurement
In the given parameters, digit 1 to 4 are used to label each of the given sport.
When such labels are used, the type of data is nominal.
Solving (b): The error 
In (a), we identified that the level of measurement is nominal. This implies that, the data are not counted, but instead they are categorized.
And as such, the mean of the data cannot be calculated.