PROBLEMS ON READING DOT PLOTS

Problem 1 :

The list shows the number of minutes it took each student in a class to present a science project.

12  10  18  20  14  14  10  18  20  10  16   14   18   16   18

Cecelia is making the dot plot shown to display the data. Which two data points does Cecelia still need to add to the dot plot?

Solution :

Let us create a frequency table, from the data given in the question

12   10  18  20  14  14  10  18  20  10  16   14   18   16   18

Comparing the frequency table and dot plot given, need to add 1 dot at 10 and 18 respectively.

Problem 2 :

The dot plots show the numbers of apples picked by members of two different tour groups at an orchard.

Which statement correctly compares these two data sets?

a) The median of the data is the same for both data sets.

b) The mode of the data is the same for both data sets.

c) The range of the data is the same for both data sets.

d) The distribution of the data is symmetrical for both data sets.

Solution :

Let us find median, mode and range from the above dot plots one by one. 

Median :

Total number of apples picked

= 1 + 2 + 2 + 1 + 4 + 3 + 2 + 2 + 3

= 20

Median will be 20/2 ==> 10^th value

5 is the median.

Mode :

Most repeated value is 5. So, mode is 5.

Range :

Range = Largest value - Smallest value

= 10 - 1

= 9

Median :

Total number of apples picked

= 2 + 1 + 2 + 3 + 4 + 4 + 6 + 3 + 3 + 2

= 30

Median will be 30/2 ==> 15^th value

7 is the median.

Mode :

Most repeated value is 7. So, mode is 7.

Range :

Range = Largest value - Smallest value

= 10 - 1

= 9

From the analysis done with above dot plots, we observe common range for both data. So, option D is correct.

Problem 3 :

The dot plot shows the number of packages mailed by the last 20 customers at a post office.

Which statement best describes the data shown in the dot plot?

a) The data distribution has gaps.

b) The data distribution is symmetrical.

c) The data are clustered at 5.

d) The peak of the data is at 10.

Solution :

The data has gaps, because there is no entry in the middle.

Problem 4 :

The list shows the lengths in centimeters of some toy boats. The length of one toy boat is missing.

5, 5, 6, 10, 8, 5, ___

Which dot plot represents the lengths of all of the toy boats?

Solution :

Creating frequency table,

5, 5, 6, 10, 8, 5

After we measure using the ruler, 10 should be repeated 2 times.

So, option D is correct.

Problem 5 :

The dot plot shows the number of tickets needed for each ride at a carnival.

What is the difference between the number of rides that need fewer than 4 tickets and the number of rides that need 4 or more tickets?

a) 7     b) 2     c) 9     d) 4

Solution :

1, 2, 3 are tickets fewer than 4.

Adding the dots in 1, 2 and 3.

2 + 5 + 4

= 11

4 or more tickets :

= 2 + 1 + 1

= 4

Difference between them = 11 - 4

= 7

So, option a is correct.