GED Math Practice Test: Statistics and Probability
- Statistics and Probability
- 10 questions
- 15 minutes
These 10 questions cover data and chance on the GED Mathematical Reasoning test: measures of center, the effect of an outlier, counting outcomes and simple and compound probability. Before choosing an answer, ask whether the order of the data or a replacement rule matters.
Tap an option to mark your answer. You can change your mind, or tap the same option again to leave the question blank. The correct answers and explanations appear when you finish the test.Tap an option to answer; tap it again to leave the question blank.
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Question 1
A store recorded the number of returns on five days: 12, 15, 9, 20 and 14. What is the mean number of returns per day?
Correct answer: B
Add the values and divide by how many there are: 70 ÷ 5 = 14. The choice 15 is the middle value of the list as written, which is not the mean.
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Question 2
What is the median of the data set 8, 3, 11, 6, 15, 9?
Correct answer: B
Put the values in order: 3, 6, 8, 9, 11, 15. With an even number of values, the median is the mean of the two middle values: (8 + 9) ÷ 2 = 8.5. The choice 8.67 is the mean of the whole set.
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Question 3
Keisha has an average score of 82 on four tests. What score does she need on the fifth test to raise her average to exactly 85?
Correct answer: C
Five tests with an average of 85 must total 85 × 5 = 425 points. Her first four tests total 82 × 4 = 328 points, so she needs 425 − 328 = 97. The choice 88 comes from simply adding the 3-point gap to 85.
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Question 4
A bag contains 5 red, 3 blue and 4 green marbles. One marble is chosen at random. What is the probability that it is not blue?
Correct answer: D
There are 12 marbles and 9 of them are not blue, so the probability is 912 = 34. The choice 14 is the probability of choosing a blue marble.
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Question 5
A fair coin is tossed and a standard six-sided number cube is rolled. What is the probability of getting heads and a 6?
Correct answer: A
The events are independent, so multiply: 12 × 16 = 112. The choice 23 comes from adding the probabilities, which is not how "and" works for independent events.
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Question 6
A box holds 4 red pens and 6 blue pens. Two pens are taken out at random, one after the other, without putting the first one back. What is the probability that both pens are red?
Correct answer: A
The first pen is red with probability 410; then 3 red pens are left among 9, so the second is red with probability 39. Multiply: 1290 = 215. The choice 425 = 410 × 410 assumes the first pen was put back.
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Question 7
A coach recorded the number of laps each runner finished: 4, 7, 7, 9, 12, 7, 15. What is the range of the data?
Correct answer: C
The range is the greatest value minus the least value: 15 − 4 = 11. The choice 7 is the mode, the value that appears most often.
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Question 8
A uniform comes in 4 shirt colors, 3 pant styles and 2 types of shoes. One shirt, one pair of pants and one pair of shoes make an outfit. How many different outfits are possible?
Correct answer: C
By the counting principle, multiply the number of choices for each part: 4 × 3 × 2 = 24. Adding the choices (4 + 3 + 2 = 9) counts items, not combinations.
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Question 9
The data set 20, 22, 25, 23, 21 has a mean of 22.2 and a median of 22. The value 80 is added to the data set. Which statement describes the change?
Correct answer: B
The new mean is 191 ÷ 6 ≈ 31.8, about 9.6 more than before. The new median is the mean of the middle values 22 and 23, which is 22.5. An outlier pulls the mean much more than the median.
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Question 10
In a survey of 200 people, 35% said they prefer tea to coffee. Of the people who prefer tea, 40% said they add sugar. How many of the people surveyed prefer tea and add sugar?
Correct answer: A
First find the tea drinkers: 200 × 0.35 = 70. Then take 40% of that group: 70 × 0.40 = 28. The choice 80 is 40% of all 200 people, not of the tea drinkers.
Questions you leave blank are not counted as wrong.
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