Data collection Terminology

Question 1

Population

Answer 1

Entire group of individuals we hope to learn about

Question 2

Sample

Answer 2

Representative subset of the population, from whom we collect data

Question 3

Parameter

Answer 3

A numerical value regarding the population.

For example, the mean income of all people in the U.S.

Question 4

Statistic

Answer 4

A numerical value for sampled date.

These are used to estimate population parameters

Question 5

Data collection

CENSUS

Answer 5

Complete enumeration of the entire population.

Attempt to contact every member of the population in order to collect data

Very cumbersome

Question 6

Data Collection

SAMPLE SURVEY

Answer 6

A study that asks questions of sample drawn from the population in hope of learning about the entire population. We study part of a population in order to make inferences about the population

Question 7

Sampling frame

Answer 7

List of individuals from whom the sample is drawn

Question 8

Methods of Sampling.

VOLUNTARY RESPONSE SAMPLE

Answer 8

Allow people to call in or respond to a poll by logging in to their computer

Question 9

Methods of sampling

CONVENIENCE SAMPLING

Answer 9

Collect data from only those who are in a convenient location or who are easy to reach

Question 10

Methods of Sampling

PROBABILITY SAMPLING

Answer 10

Uses randomization in order to eliminate some of the Biases of voluntary and conveniene sampling

Valid

Question 11

Types of probability samples

SIMPLE RANDOM SAMPLE

Answer 11

Each person has the same chance of being selected

All possible combinations of n have the same chance of being selected

Question 12

Types of probability samples

STRATIFIED RANDOM SAMPLE

Answer 12

Population is divided into strata(subgroups) which are more homogeneous. Then choose an SRS from each strata.

For example, high school students are first divided into 4 strata (freshmen, sophs, juniors, seniors) then an SRS is taken from each.

(differs from SRS in that not all possible combinations of size n can be used for the sample)

Question 13

Types of probability samples

SYTEMATIC RANDOM SAMPLE

Answer 13

First person selected randomly and then followed by a system.

For example if we want a sample of 10 out of pop. of 400,
Select random number from 1-40, say 32. Then add intervals of 40… so we would use 32, 72, 112, 152, 192,…

Question 14

Types of probability samples

CLUSTER RANDOM SAMPLE

Answer 14

A sampling design in which entire groups or clusters are chosen at random. Each cluster should be heterogeneous, that is, include a range if people representing the various segments of the population

Question 15

Types of probability samples

MULTISTAGE RANDOM SAMPLE

Answer 15

Sample is chosen in a series of stages. This type of sample is used extensively in national polls.
Example: Start with SRS of the counties in U.S., from set of counties, take srs of towns, from set of towns take srs of neighborhoods, from which take srs of households…
Statistucal methods are adjusted for different types of sampling

Question 16

Biases

Answer 16

Sytematic error that favors a particular segment of the population or tends to encourage only certain outcomes in the data. These can be due to a poor methid if sampling, or even if the sampling is good, the data collection may have problems.

Question 17

VOLUNTARY RESPONSE BIAS

Answer 17

Bias introduced when individuals can choose whether or not to participate in the sample. Samples based on voluntary response are always invalid

Question 18

NONRESPONSE BIAS

Answer 18

people refuse to respond or can’t be reached. Those who do respond are likely not to represent the whole sample. Voluntary response bias is a type of nonresponse bias, but nonresponse can also occur because people are unavailable.

Question 19

UNDERCOVERAGE BIAS

Answer 19

A group of people are underrepresented, such as people without phones or people not home during the day (related to selection bias)

Question 20

RESPONSE BIAS

Answer 20

Anything in a survey that influences responses. Peple can respond in a certain way due to wirding if questions, order of choices, appearance of the interviewer, or dishonesty.

Question 21

SAMPLING ERROR

Answer 21

NAtural VAriation between samples. It is Always present and can be described using probability. It is generally smaller when the sample size is larger.
It is NOT an indication of something done incorrectly or of bias - it’s just chance variation.