Statistics

By the addition rule for probabilities, P(A∪B)=P(A)+P(B)−P(A∩B). Substituting 0.4, 0.5, and 0.2 gives 0.4+0.5−0.2=0.7, so answer B is correct. Choice A (0.6) often results from adding the three numbers without subtracting the overlap, which overestimates the union and therefore gives a higher value than the true probability.

The eight numbers sorted are 1,1,2,3,4,5,6,9; with an even count the median is the average of the fourth and fifth terms, (3+4)/2 = 3.5, making answer B correct. Choice A treats the median as a single middle value, which is only valid for an odd number of data points.

The mean is calculated by summing all five values to get 75 and then dividing by the total count of 5, which yields 15. A diagram for this topic isn't available yet — the worked example below walks the same reasoning step by step.

• !Option A is incorrect because 12 is too low and does not represent the central balance point of this symmetric arithmetic progression.
• !Option C is incorrect because 2 represents the actual data values, not the spread of the data.

Answer each from memory — you'll see instantly whether you're right and why.

Run a focused 10-question mini-mock on Statistics and see it stick.