Statistics Chapters 1-6

Front 1

Individuals

Back 1

The objects described by a set of data. Individuals may be people, animals or things

Front 2

Variable

Back 2

is any characteristic of an individual. A variable can take different values for different individuals.

Front 3

OBservational study

Back 3

observes indivviduals and measures variables of interest but does not attempt to influence the responses

Front 4

Purpose of observational study

Back 4

to describe some group or situation

Front 5

Population

Back 5

in a statistical study is the entire group of individuals about which we want information

Front 6

Sample

Back 6

a part of the population from which we actually collect information and is used to draw conclusions about eh whole.

Front 7

Census

Back 7

is a sample survey that attempts to include the entire population in the sample

Front 8

Experiment

Back 8

delibertely imposes some tretment on individuals inorder to observe their responses.

Front 9

The purpose of an experiment

Back 9

to study whether the treatment causes a change in the response

Front 10

convenience sampling

Back 10

selection of whichever individuals are easiest to reach

Front 11

voluntary response sample

Back 11

chooses itself by responding to a general appeal. write-in or call-in polls are examples.

Front 12

simple random sample (SRS)

Back 12

of size n consists of n individuals from the population chosen in such a way that every set of n individuals has an equal cance to be the sample actually selected

Front 13

table of random digits

Back 13

is a long string of the digits 0,1,....9 withe these 2 properties. 1) each entry in the table is equally likely to be any of the 10 digits. 2) the entries are idependent of each other.

Front 14

parameter

Back 14

a number that describes the population. It is a fixed number, but in practice we don't know the value

Front 15

Statistic

Back 15

is a number that describes a sample. The value of a statistic is known when we have taken a sample, but it can change from smaple to sample. we often use a statistic to estimate an unknown parameter.

Front 16

what are the two types of errors in estimation

Back 16

bias and variability

Front 17

Bias

Back 17

is consistent, repeated deviation of the sample statistic from the population parameter in teh same direction when we take many samples

Front 18

Variability

Back 18

describes how spread out the values of the sample statistic are when we take many samples. large variability means that the result of sampling is not repeatable.

Front 19

how do you reduce bias

Back 19

use random sampling

Front 20

how do you reduce variability of an SRS

Back 20

use a larger sample

Front 21

confidence statements

Back 21

has 2 parts. margin of error and a level of confidence.

Front 22

the conclusion of a confidence statement always applies to the...

Back 22

population NOT to the sample. We know what the sample thinks as they were the ones interviewed.

Front 23

undercoverage

Back 23

occurs when some groups in the population are left out of the process of choosing the sample

Front 24

non-response

Back 24

is the faiure to obtain data from an individual selected for a sample. Most nonresponse happens because some subjects can't be contacted or b/c some subjects refuse to cooperate.

Front 25

response variable

Back 25

a variable that measures anoutcome or result of a study

Front 26

explanatory variable

Back 26

a variable taht we think explains or causes changes in the response variables.

Front 27

sampling error

Back 27

errors caused by the act of taking a sample. They cause sample results to be different fromt the results of a census

Front 28

Random sampling error

Back 28

is the deviation between the sample statistic and the population parameter caused by a chance in selecting a random sample. The MOE in a confidence statement includes ONLY random sampling error

Front 29

nonsampling errors

Back 29

are errors not related to the act of selecting a sample from the population. The can be present even in a census

Front 30

undercoverage/sampling error

Back 30

occurs when some groups in the population are left out of the process of choosing the sample.

Front 31

processing error/nonsampling error

Back 31

mistakes in mechanical taskes such as math or data entry

Front 32

response error/nonsampling error

Back 32

subject gives an incorrect response

Front 33

nonresponse/nonsampling error

Back 33

is the failure to obtain data from an individual selected for a sample. nmost nonresponse happens b/c some subjects can't be contacted or because some subjects who are refuse to cooperate

Front 34

stratified sample

Back 34

divide the sampling frame into distince groups of individuals called STRATA
take a separate SRS

Front 35

probability sample

Back 35

a sample chosen by chance

Front 36

response variable

Back 36

a variable that measures an outcome or result of a study

Front 37

explanatory variable

Back 37

variable that we think explains or causes changes in the response variable

Front 38

subjects

Back 38

the individuals studied in an experiment

Front 39

treatment

Back 39

specific experimental condition applied to the subjects. If an experiment has several explanatory variables, a treatment is a combination of specific values of these variables

Front 40

lurking variable

Back 40

a variable that has an important effect on the relationship among the variables in a study but is not one of the explanatory variables studied

Front 41

confounded

Back 41

effects on a response variable cannot be distinguished from another variable. may be either explanatory variables or lurking variables.

Front 42

principles of experimental design

Back 42

control the effects of lurking variables on the response, most simply by comparint 2 or more treatments.
randomize-use impersonal chance to assign subjects
Use enough subjects

Front 43

statistical significance

Back 43

an observed effect of a size that would rarely occur by chance

Front 44

double-blind experiment

Back 44

neither the subject nor the people who work with them know which treatment each subject is receiving

Front 45

nonadherers

Back 45

subjects who participate but don't follow the experimental treatment

Front 46

completely randomized

Back 46

all the experimental subjects are allocated at random among all the treatments

Front 47

matched pairs design

Back 47

compares just two treatments.

Front 48

block
block design

Back 48

a group of experimetnal subjects that are known before the experiment
the random assignment of subjects to treatments is carried out separately w/i each block