Chapter 2: Data Collection

Question 1

Observation

Answer 1

A single member of a collection of items that we want to study, such as a person, firm, or region

Question 2

Variable

Answer 2

Characteristic of the subject or individual, such as an employee’s income or an invoice amount

Question 3

Data set

Answer 3

Consists of all the values of the variables for all of the observations we have taken as a whole

Question 4

Data

Answer 4

Used as a plural. Data usually are entered into a spreadsheet or database as an n x m matrix

Specifically, each column is a variable (m columns) and each row is an observation (n rows)

Question 5

Univariate data sets

Answer 5

Data sets with one variable

Question 6

Bivariate data sets

Answer 6

Data sets with two variables

Question 7

Multivariate data sets

Answer 7

Data sets with more than two variables

Question 8

Types of data - Categorical

Answer 8

Qualitative.
Values that are described by words rather than by numbers.

Verbal label such as vehicle type, pay type )car, truck , salary, hourly, etc) or coded (1, 2, 3 )

Question 9

Types of data - Numerical

Answer 9

Quantitative.
Values that are described by numbers rather than words, such as counting, measuring something.

Discrete (ie. broken eggs in a carton, annual dental visits) or Continuous (patient waiting time or customer satisfaction percentages)

Question 10

Coding

Answer 10

When values of categorical variable are represented using numbers.

Ie. 1 = cash 2 = check 3 = credit etc

Question 11

Binary variables

Answer 11

Categorical variables that only have two values

Question 12

Discrete

Answer 12

A variable with a countable number of distinct values

Question 13

Continuous

Answer 13

A numerical variable that can have any value within an interval

Question 14

Time series data

Answer 14

If each observation in the sample represents a different equally spaced point in time (years, months, days)

Question 15

Periodicity

Answer 15

The time between observations

Question 16

Cross- sectional data

Answer 16

If each observation represents a different individual unit (a person, firm, geographic area) at thee same point in time

Question 17

Sample

Answer 17

A subset of the population that we will actually analyze

Question 18

Population

Answer 18

All of the items that we are interested in

Question 19

Census

Answer 19

An example of all items in a defined population.

A sample involves looking only at some items selected from the population while the census is an examination of all the items.

Question 20

Parameter

Answer 20

A measurement or characteristic of the population (eg. a mean or a proportion) Usually unknown because we can rarely observe the entire population.

Question 21

Statistic

Answer 21

A numerical value calculated from a sample (eg. a mean or proportion)

Question 22

Target population

Answer 22

Contains all the individuals in which we are interested

Question 23

Sampling frame

Answer 23

The group from which we take the samples (ex. are phone directories, voter registration lists, alumni associations mailing lists, or marketing databases)

Question 24

Random sampling

Answer 24

Items are chosen by randomization or a chance procedure

Question 25

Non-random sampling

Answer 25

Less scientific but it is sometimes used for expediency

Question 26

Simple random sample

Answer 26

Every item in the population of N items has the same chance of being chosen in the sample of n items

Question 27

Random number

Answer 27

A sampling to chose at random

Excels function =RANDBETWEEN(1,4) or any set of numbers

Question 28

Sampling without replacement

Answer 28

Once an item has been selected to be included in the sample, it can not be considered for the sample again

Question 29

Sampling with replacement

Answer 29

Once an item has been selected, it can be selected again

=RANDBETWEEN (a,b) function uses sampling with replacement

Question 30

Infinite population

Answer 30

When the sample is less than 5 percent of the population (ie. when n/N is less than or equal to .05), then the population is effectively infinite.

An equivalent statement is that a population is effectively infinite when it is at least 20 times as large as the sample (or when N/n is more than or equal to 20)

Question 31

Systematic sampling

Answer 31

Choosing every kth item from a sequence or list, starting from a randomly chosen entry among the first k items on the list

A systematic sample of n items from a population of N items requires the periodicity k be approximately N/n

Question 32

Strata

Answer 32

Homogeneous subgroups of known size

Question 33

Stratified sampling

Answer 33

Within each stratum, a simple random sample of the desired size could be taken.

Alternatively, a random sample of the whole population could be taken, and then individual strata estimates could be combined using appropriate weights

Question 34

Cluster samples

Answer 34

Taken from strata consisting of geographical regions

We divide a region (a city) into sub regions (blocks, subdivisions, school districts)

Question 35

Judgement sampling

Answer 35

Non-random sampling method that relies on the expertise of the sampler to choose items that are representative of the population

Question 36

Convenience sampling

Answer 36

Quick. Grabbing whichever sample is available and handy.

Question 37

Focus group

Answer 37

A panel of individuals chosen to be representative of a wider population, formed for open-ended discussion and idea gathering about an issue

Question 38

Non-response bias

Answer 38

Occurs when those who respond have characteristics different from those who don’t respond

Question 39

Selection bias

Answer 39

Self selected samples, ie someone who volunteers for a survey

Question 40

Response error

Answer 40

Occurs when respondents deliberately give false information to mimic socially acceptable answers, to avoid embarrassment, or protect personal information

Question 41

Coverage error

Answer 41

Occurs when some important segment of the target population is systematically missed

Question 42

Measurement error

Answer 42

Results when the survey questions do not accurately reveal the construct being assessed

Question 43

Interviewer error

Answer 43

When the interviewer’s facial expressions, tone of voice, or appearance influences the responses

Question 44

Sampling error

Answer 44

Uncontrollable random error that is inherent in any random sample

Question 45

Valid survey

Answer 45

A survey that measures what the researcher wants to measure

Question 46

Reliable survey

Answer 46

A survey that is consistent. In other words, will the responses from similar respondents stay the same over time?