Answer:
The frequency is 3 more than expected
Explanation:
There are 3 favourable outcomes: {2, 4, 6}
There are 6 possible outcomes: {1, 2, 3, 4, 5, 6}
probability of the number cube landing on an even number = favourable outcomes / possible outcomes = 3/6 = 1/2
If the cube is rolled 30 times, it is expected that in 1/2*30 = 15 times landed on an even number. The frequency: 18 is 3 more than expected