Types of Variables
Percentages and Tables
Measurements of Central Tendency
Ch. 3 Questions
100
Whether someone in the household owns a smart phone is what kind of variable?
Categorical
100
A categorical variable has three categories, with the frequencies of occurrence below.
Category Frequency
A 28
B 14
C 8
Calculate the percentages of each category
56%, 28%, 16%
100
The following is a set of data from a sample of n = 5.
3, 1, 10, 2, 9
a. Compute the mean, median, and mode.
5, 3, no mode
100
How do we find outliers by using the z-score test?
If test result is greater than +3 or -3, there is an outlier
200
Number of text messages exchanged per month is what kind of variable?
Discrete Numerical
200
The accompanying table contains the 2018 sources of
electricity in the United States as reported by the Energy
Information Administration.
Source Billion kWh
Coal 1146
Biomass 63
Natural gas 1468
Nuclear 807
Other sources 323
Petroleum coke and liquids 26
Solar 67
Wind 275
Calculate percentages
(In order)
27.4%, 1.5%, 35.2%, 19.3%, 7.7%, 0.6%, 1.6%, 6.6%
200
The following is a set of data from a sample of n = 5.
2, − 8, − 5, 2, 6
a. Compute the mean, median, and mode.
-0.6, 2, 2
200
What is thee difference between variance and standard deviation if we use sample notation.
Variance uses s2 and standard deviation uses s
300
Length (in minutes) of the longest telephone call made in a day is what kind of variable?
Continuous Numerical
300
The data below represent the responses to two questions asked in a survey of college students majoring in business:
What is your gender? and What is your major?
(M = male; F = female) (A = Accounting; C = Computer Information Systems;M = Marketing).
Gender: F F M F F M F F F M
Major: M M M A C A C A A C
Gender: M M F M F F M F M F
Major: M A M A A C A M C M
Gender: M M M F F F F M F F
Major: A M A M A M A M C A
Gender: F F M F M F F M M F
Major: C M A C C C M M C M
Construct a contingency table
Student Major Categories
Gender A C M Totals
Male 7 4 5 16
Female 7 7 10 24
Totals 14 11 15 40
300
What is the formula to calculate the median?
(n + 1) ÷ 2}th
300
What does it mean to have right-skewed data?
Mean is greater than median
400
Time, in hours, spent shopping online per week is what kind of variable?
continuous numerical
400
Compute the percentages of the previous table
Student Major Categories
Gender A C M Totals
Male 7 4 5 16
Female 7 7 10 24
Totals 14 11 15 40
Gender A C M Totals
Male 17.5 % 10.0 % 12.5 % 40.0 %
Female 17.5 17.5 25.0 60.0
Totals 35.0 27.5 37.5 100.0
400
What is the formula to calculate the mean?
400
How do you calculate IQR?
IQR= Q3 - Q1
500
One of the variables most often included in surveys is income. Sometimes the question is phrased "What is your income (in
thousands of dollars)?"
Explain why income might be considered either discrete or continuous.
Income in thousands of dollars can be considered discrete because the number of thousands of dollars of in
amounts between each thousand that can be measured to different levels of precision.
500
What is the percentage of accounting majors?
What is the percentage of females?
35%, 60%
500
Carrier Download Speed Upload Speed
Verizon 53.3 17.5
AT&T 37.1 12.9
Straight Talk 31.1 15.6
Boost 29.4 3.7
T-Mobile 36.3 16.9
Cricket 6.5 5.8
The mean download speed is 32.28 Mbps.
The mean upload speed is 12.07 Mbps.
The median download speed is 33.70 Mbps.
The median upload speed is 14.25 Mbps.
No modes
500
What does the Z score measure?
The number of standard deviations from the mean