The random variable is determined by chance and can be discrete or continuous. Since the mean is numerical at 1.5, the random variable will also be numerical. It's not possible to tell from the mean whether the random variable is discrete (normally an integer representing, for example, a count or score in a test) or continuous. The mean is simply the sum of the data divided by the number of items of data. If the sum of integer data is 15 and there are 10 items, the mean will be 1.5. If the data is, for example, the length of macaroni and there are 20 pieces, the average length does not tell us whether the individual lengths are integers. It's likely that they won't be: lengths such as 1.24, 1.75, 1.3 can still add up so that the mean is 1.5. In the case of macaroni the random variable is continuous.