NJSLA NJSLA Data Analysis and Statistics 3

Question 1

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?

Accepted Answer

1/2

Answer

There are 5 blue marbles out of 10 total, so the probability is 5/10 = 1/2.

Question 2

A stem-and-leaf plot shows stems 4, 5, 6, 7 with leaves 2 3 | 1 5 9 | 0 4 | 3. How many data values are in the 50s?

Accepted Answer

3

Answer

The stem 5 has leaves 1, 5, and 9, representing values 51, 55, and 59 — three values in the 50s.

Question 3

Which of the following best describes a situation where two events are independent?

Accepted Answer

Flipping a coin twice, where the result of the first flip does not affect the second

Answer

Two events are independent when the outcome of one does not change the probability of the other, as in flipping a coin twice.

Question 4

A data set has a mean of 50 and a standard deviation of 5. A value of 65 is how many standard deviations above the mean?

Accepted Answer

3

Answer

The z-score is (65 − 50) / 5 = 15 / 5 = 3 standard deviations above the mean.

Question 5

On a dot plot, several dots are stacked at the value 7, and the rest are spread between 1 and 5. What does the cluster at 7 suggest?

Accepted Answer

7 is the most frequent value in the data set.

Answer

A stack of dots at a single value on a dot plot shows that value was observed multiple times, making it the most frequent.

NJSLA Exam Practice Test