Statistics and Probability Practice Questions
Common Core (US) · Common Core Math Grade 8 · 147 free MCQs with instant results and detailed explanations.
147
Total
50
Easy
76
Medium
21
Hard
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Sample Questions from Statistics and Probability
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Q1
Easy
A school surveyed students about their favorite subject. If 20 students chose Math, 15 chose Science, and 10 chose English, what is the probability that a randomly chosen student prefers Math?
A.
0.5
B.
0.4
C.
0.2
D.
0.25
Show Answer & Explanation
Correct Answer: B
The total number of students is 20 + 15 + 10 = 45. The probability of choosing a student who prefers Math is the number of Math preferences (20) divided by the total number of students (45), which is 20/45 = 0.4.
Q2
Easy
In a box of 30 balls, there are 12 red balls, 8 blue balls, and 10 green balls. What percentage of the balls are red?
A.
30%
B.
40%
C.
25%
D.
20%
Show Answer & Explanation
Correct Answer: B
To find the percentage of red balls, divide the number of red balls (12) by the total number of balls (30) and multiply by 100. So, (12/30) * 100 = 40%.
Q3
Easy
If the median of the data set {12, 3, 5, 8, 10} is 8, what is the correct order of this data set when arranged from least to greatest?
A.
{3, 5, 8, 10, 12}
B.
{12, 10, 8, 5, 3}
C.
{10, 8, 5, 3, 12}
D.
{5, 3, 10, 12, 8}
Show Answer & Explanation
Correct Answer: A
To find the median correctly, you must first arrange the data in ascending order. The ordered set is {3, 5, 8, 10, 12}, and the middle number is indeed 8.
Q4
Medium
In a data set, the numbers are: 12, 15, 12, 18, 20, 12, 25. What is the mode of this data set?
A.
12
B.
15
C.
18
D.
20
Show Answer & Explanation
Correct Answer: A
The mode is the number that appears most frequently in a data set. Here, 12 appears four times, while all other numbers appear less frequently. Thus, the mode of this data set is 12.
Q5
Medium
A teacher records the heights of students in a class, with a mean height of 160 cm and a standard deviation of 10 cm. If a student is 180 cm tall, how many standard deviations above the mean is this student?
A.
1
B.
2
C.
3
D.
4
Show Answer & Explanation
Correct Answer: B
To find how many standard deviations above the mean a value is, subtract the mean from the value and divide by the standard deviation. Here, (180 - 160) / 10 = 20 / 10 = 2. Therefore, the student is 2 standard deviations above the mean.
Q6
Medium
A group of students surveyed their favorite types of pets. The results are as follows: 12 prefer dogs, 8 prefer cats, 5 prefer birds, and 10 prefer fish. What is the mode of this data set?
A.
Dogs
B.
Fish
C.
Cats
D.
Birds
Show Answer & Explanation
Correct Answer: A
The mode is the value that appears most frequently in a data set. Here, dogs (12) are preferred by the most students compared to other pets.
Q7
Medium
A data set has the values: 5, 7, 9, 5, 6, 8, 6. What is the median of this data set?
A.
6
B.
5.5
C.
7
D.
8
Show Answer & Explanation
Correct Answer: A
To find the median, arrange the numbers in ascending order: 5, 5, 6, 6, 7, 8, 9. The middle value is 6, as it is the 4th number in a list of 7.
Q8
Hard
A class has 24 students. If the teacher wants to divide them into groups of 4 for a project, how many different ways can the teacher choose these groups, assuming the order of selection does not matter?
A.
126
B.
64
C.
12
D.
6
Show Answer & Explanation
Correct Answer: A
To determine how many ways you can choose groups of students, you use the combination formula nCr = n! / (r!(n-r)!), where n is the total number of students and r is the size of the groups. Here, n = 24 and r = 4. The calculation gives 24! / (4!(24-4)!) = 126.
Q9
Hard
In a normal distribution of test scores, the mean score is 75 with a standard deviation of 10. What is the z-score for a test score of 85?
A.
0.5
B.
1.0
C.
1.5
D.
2.0
Show Answer & Explanation
Correct Answer: B
The z-score is calculated using the formula z = (X - μ) / σ, where X is the test score, μ is the mean, and σ is the standard deviation. For a score of 85, z = (85 - 75) / 10 = 1.0.
Q10
Hard
A school surveyed students about their favorite type of music. The results were: Pop - 30%, Rock - 25%, Hip-Hop - 20%, Classical - 15%, Other - 10%. If 200 students participated, how many students preferred Pop music?
A.
60
B.
70
C.
75
D.
80
Show Answer & Explanation
Correct Answer: A
To find the number of students who preferred Pop music, we calculate 30% of 200. This is done by multiplying 200 by 0.30, which equals 60.
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Statistics and Probability — Common Core (US) Common Core Math Grade 8 Practice Questions Online
This page contains 147 practice MCQs for the chapter Statistics and Probability in Common Core (US) Common Core Math Grade 8. The questions are organized by difficulty — 50 easy, 76 medium, 21 hard — so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.