Module 1 (Ch. 1-3)

Question 1

Population

Answer 1

All of the entities of interest in a study (ppl, households, machines, etc.)

Question 2

Sample

Answer 2

A subset of the population, often randomly chosen and representative of the pop as a whole

Question 3

Data Set

Answer 3

A rectangular array of data

Question 4

Variable

Answer 4

Aka Field or Attribute A characteristic of members of a population (height, gender, salary) ROW (left to right)

Question 5

Observation

Answer 5

Aka Case or Record A list of all variable values for a single member of a population COLUMN (up and down)

Question 6

Numerical Variable

Answer 6

A variable where meaningful arithmetic can be performed on (age, children, salary)

Question 7

Categorical Variable

Answer 7

A variable where NO meaningful arithmetic can be performed. (gender or state) Can either be ORDINAL or NOMINAL. Can be coded numerically or left uncoded. Opinion Variables - “strongly disagree”

Question 8

Date Variable

Answer 8

Treated differently from typical numbers

Question 9

Ordinal (Categorical Variable)

Answer 9

There is a natural ordering of its possible values

Question 10

Nominal (Categorical Variable)

Answer 10

No natural ordering of its possible values

Question 11

Dummy Variable

Answer 11

0 - 1 coded variable for a specific category (1 for all in the category, 0 for all not in the category)

Question 12

Binned or Discretized Numerical Variable

Answer 12

Categorizing a NUMERICAL variable by putting data into discrete categories (called BINS)

Question 13

Discrete Numerical Variable

Answer 13

If it results from a count (number of children)

Question 14

Continuous Variable

Answer 14

Essentially continuous measurement (weight or height)

Question 15

Cross-Sectional Data

Answer 15

Data on a cross sections of a population at a distinct point in time

Question 16

Time Series

Answer 16

Data collected over time.

Question 17

Count of Categories

Answer 17

Count the number of observations (columns) in each category

Question 18

Mean

Answer 18

The average of all values. In Excel…Average Function

Question 19

Sample Mean

Answer 19

A sample from some larger pop. Denoted by a X with a line above.

Question 20

Population Mean

Answer 20

Represents the entire population. Denoted by a “U”

Question 21

Median

Answer 21

Middle observation when data is sorted from smallest to largest. In Excel…Median Function

Question 22

Mode

Answer 22

The value that appears most often. In Excel….Mode Function

Question 23

Range

Answer 23

A measure of Variability (flexibility).

Maximum value minus minimum value.

Very sensitive to extreme values

Question 24

Interquartile Range (IQR)

Answer 24

3rd quartile minus 1st quartile.

Less sensitive to extreme values

Question 25

Variance

Answer 25

the average of the squared deviations from the mean ex: (x - mean)²

Question 26

Sample Variance

Answer 26

Denosted by s²

Question 27

Population Variance

Answer 27

Denotd by O²

Question 28

Standard Deviation

Answer 28

The square root of variance

Question 29

Sample Standard Deviation

Answer 29

Denoted by s, the square root of the sample variance

Question 30

Population Standard Deviation

Answer 30

Denoted by "o", the square root of the population variance

Question 31

Emperical Rules

Answer 31

The values of a variable are approximately "normally" distributed - 68% within one standard deviation - 95% within two standard deviations - 99.7% within three standard deviations

Question 32

Mean Absolute Deviation (MAD)

Answer 32

The average of the absolute deviations Emperical Rule : for many variables, the standard deviation is approximeatley 25% larger than MAD

Question 33

Skewness

Answer 33

Occurs when there is a lack of symmetry.

Question 34

Skewed to the Right

Answer 34

A variable can be POSITIVELY scewed because of really large values (ex: large baseball salaries)

Question 35

Skewed to the Left

Answer 35

Negatively Skewed Can be skewed to the left because of small values (ex: temp. lows in Antartica)

Question 36

Kurtosis

Answer 36

"fatness" of the tails of the distribution relative to the tails of a normal distribution. High Kurtosis has many more extreme observations.

Question 37

Histogram

Answer 37

Most common type of chart for showing the distribution of a numerical variable/CROSS SECTIONAL VARIABLE. Based on binning the variable. A column chart of the counts in the various categories. Great for showing the shape of a distribution.

Question 38

Box Plot

Answer 38

Used for CROSS SECTIONAL VARIABLES aka Box-Whisker Plot an alternative type of chart for showing the distribution of cross-sectional variables.

Question 39

Time Series Graph

Answer 39

Main interest is to see how variables change over time.

Question 40

Outlier

Answer 40

a value or an entire observation (row) that lies well outside of the norm

Question 41

Filtering

Answer 41

finding records that match particular criteria

Question 42

Crosstabs

Answer 42

aka Contingency Table a way to examine relationships between two categorical variables through counts and corresponding charts of the counts

Question 43

Comparison Problem

Answer 43

When you want to compare a numerical measure across two or more subpopulations

Question 44

Trendline

Answer 44

a line or curv that fits the scatterplot