Knewton Alta - Chapter 2 - Descriptive Statistics Exam Questions with Verified Solutions Rated 100%
Find the mode of the following amounts (in thousands of dollars) in checking accounts of randomly
selected people aged 20-25.
2,4,4,7,2,9,9,2,4,4,11 - Answers If we count the number of times each value appears in the list, we get
the following frequency table:
Note that 4 occurs 4 times, which is the greatest frequency, so 4 is the mode of the amounts (in
thousands of dollars) in checking accounts of randomly selected people aged 20-25.
Given the frequency table below for a list of recorded lengths (in inches) of randomly sampled garden
snakes, find the mean.
V-F
9-8
10-3
11-2
12-2
13-1
14-1
15-3 - Answers Remember that the mean is the sum of all the numbers divided by the number of
numbers. The frequency table tells you the number of time that each number appears in the set of data.
So to get the sum of all the numbers in the set of data, we take each frequency multiplied by its value
and add them all up:
Sum=9⋅8+10⋅3+11⋅2+12⋅2+13⋅1+14⋅1+15⋅3=72+30+22+24+13+14+45=220
The number of numbers in the list is the sum of the frequencies.
Number of numbers=8+3+2+2+1+1+3=20
So the mean of the recorded lengths (in inches) of randomly sampled garden snakes is
SumNumber of numbers=22020=11
Elliot likes to find garden snakes in his backyard and record their lengths. Estimate the mean of the
lengths (in inches) of the garden snakes given in the following grouped frequency table.
Round the final answer to one decimal place. - Answers 11.5
,Remember that to estimate the mean, we first find the midpoint of each interval:
MidpointFrequency5.579.5613.51217.55
Now, we treat this as if it were a regular frequency table. We take each midpoint multiplied by its
frequency, add them up, and divide by the total number of values. The sum is
5.5⋅7+9.5⋅6+13.5⋅12+17.5⋅5=345
We find the total number of values by adding up the frequency column:
7+6+12+5=30
Finally, dividing the sum by the total number of values, we find our mean estimate of the lengths (in
inches) of the garden snakes is:
Mean estimate=34530=11.5
Jon loves to go bird watching at a nearby animal sanctuary. Find the mean of the following numbers of
birds he spotted at the sanctuary in the last few days.
14,10,17,11,9,15,6,14 - Answers Remember that the mean is the sum of the numbers divided by the
number of numbers. There are 8 numbers in the list. So we find that the mean number of birds spotted
is
14+10+17+11+9+15+6+14////8 = 96
96/8 = 12
Given the following frequency table of values, is the mean or the median likely to be a better measure of
the center of the data set - Answers Most of the values are close together in the range between 33 and
37, but because there is one number, 20, which is much smaller than the rest of the values, the median
is probably a better measure of the center of this data set.
A music teacher would like to find the mean number of songs people listen to on the way home from
work. She collects data from 18 teachers at the school. The graph shows the frequency for the number
of songs the teachers listen to on their way home from work.
Find the mean number of songs listened to for the 18 teachers, and round your answer to the nearest
tenth. Record your answer by dragging the purple point to the mean. - Answers The frequency graph
shows the frequency for each data value. So, we can compute the mean by adding up all the data values
and dividing by the total number of data values.
0⋅1+1⋅2+2⋅3+2⋅4+3⋅5+2⋅6+8⋅71///8=99/18=5.5.
Rounding to the nearest tenth, we have the mean is 5.5.
, Find the median of the numbers in the following list.
10,7,15,6,24,20,1 - Answers It helps to put the numbers in order.
1,6,7,10,15,20,24
Now, because the list has length 7, which is odd, we know the median number will be the middle
number. In other words, we can count to item 4 in the list, which is 10. So the median is 10.
Find the median of the following list of dollars spent per customer at a cheese shop in the last hour.
32,19,21,16,27,15 - Answers It helps to put the numbers in order.
15,16,19,21,27,32
Now, because the list has length 6, which is even, we know the median number will be the average of
the middle two numbers, 19 and 21. So the median number of dollars spent per customer at a cheese
shop in the last hour is 20
Find the mode of the following amounts of exercise (in hours) randomly selected runners completed
during a weekend.
2,14,14,4,2,4,1,14,4,4,8 - Answers Note that 4 occurs 4 times, which is the greatest frequency, so 4 is the
mode of the amount of exercise (in hours) randomly selected runners completed during a weekend.
Given the following frequency table of values, is the mean or the median likely to be a better measure of
the center of the data set? - Answers Median
Most of the values are close together in the range between 40 and 45, but because there is one number,
70, which is much larger than the rest of the values, the mean would not be a good measure because
that one large value would pull the mean up. Therefore, the median is probably a better measure of the
center of this data set.
Find the mode of the following number of times each machine in a car factory needed to be fixed within
the last year.
2,5,6,12,14,12,6,2,5,3,14,5 - Answers Note that 5 occurs 3 times, which is the greatest frequency, so 5 is
the mode of the number of times a machine in a car factory needed to be fixed within the last year
Find the mode of the following number of states randomly selected travelers at a service plaza visited in
the past three years.
18,13,8,8,13,10,13,10,9,18 - Answers Note that 13 occurs 3 times, which is the greatest frequency, so 13
is the mode of the number of states randomly selected travelers at a service plaza visited in the past
three years.
Find the median of the following set of data.
