NJGPA Statistics, Data Analysis, and Probability 1 — Questions and Answers
Question 1: A data set has the values: 4, 7, 7, 9, 13. What is the mean of this data set?
- 7
- 8 (Correct answer)
- 9
- 10
Correct answer: 8
The mean is found by adding all values (4+7+7+9+13=40) and dividing by the count (40÷5=8).
Question 2: A bag contains 3 red marbles, 5 blue marbles, and 2 green marbles. If one marble is drawn at random, what is the probability it is blue?
- 1/5
- 1/2 (Correct answer)
- 3/10
- 2/5
Correct answer: 1/2
There are 5 blue marbles out of 10 total (3+5+2=10), so the probability is 5/10 = 1/2.
Question 3: Which measure of central tendency is most affected by an extreme outlier in a data set?
- Mode
- Median
- Mean (Correct answer)
- Range
Correct answer: Mean
The mean uses all values in its calculation, so an extreme outlier pulls it significantly higher or lower.
Question 4: A scatter plot shows a trend where as x increases, y also increases consistently. What type of correlation does this represent?
- Negative correlation
- No correlation
- Positive correlation (Correct answer)
- Inverse correlation
Correct answer: Positive correlation
When both variables increase together, the data shows a positive correlation.
Question 5: The following scores were recorded: 65, 70, 70, 75, 80, 85, 95. What is the median?
- 70
- 74
- 75 (Correct answer)
- 80
Correct answer: 75
When 7 values are listed in order, the median is the 4th value: 65, 70, 70, 75, 80, 85, 95 — so the median is 75.
Question 6: A student surveys 30 classmates about their favorite subject and displays the data in a bar graph. What type of data did the student collect?
- Quantitative continuous data
- Quantitative discrete data
- Qualitative categorical data (Correct answer)
- Numerical interval data
Correct answer: Qualitative categorical data
Favorite subject is a category, not a number, making it qualitative (categorical) data.
Question 7: A box plot shows a minimum of 20, Q1 of 35, median of 50, Q3 of 65, and a maximum of 80. What is the interquartile range (IQR)?
- 30 (Correct answer)
- 60
- 15
- 50
Correct answer: 30
The IQR is Q3 minus Q1: 65 − 35 = 30.
NJGPA Statistics, Data Analysis, and Probability 1
A data set has the values: 4, 7, 7, 9, 13.
What is the mean of this data set?