Vocabulary of StatisticsVocabulary of Statistics

Part 3Part 3

Data Collection - SurveysData Collection - Surveys TelephoneTelephone pros: less costly, more candidpros: less costly, more candid

cons: no phone, no call listcons: no phone, no call list Mailed questionnaireMailed questionnaire pros: cover more area, less costpros: cover more area, less cost cons: low response, inappropriate cons: low response, inappropriate

responsesresponses Personal InterviewPersonal Interview

pros: in-depth responses,pros: in-depth responses, cons: training, cost, biascons: training, cost, bias

Other methods of data collectionOther methods of data collection

ObservationObservation

directdirect

indirectindirect

surveying recordssurveying records

Four Methods of SamplingFour Methods of Sampling

RandomRandom SystematicSystematic StratifiedStratified ClusterCluster

RandomRandom

selected by using chance methods or selected by using chance methods or random numbersrandom numbers

put everybody’s name in a bucket and put everybody’s name in a bucket and choosechoose

assign a number, use a random number assign a number, use a random number generatorgenerator

SystematicSystematic

Number each subject of the Number each subject of the population, then select every population, then select every nthnth subject.subject.

example: 1600 kids at MHS. We example: 1600 kids at MHS. We want a sample of 200. 1600 want a sample of 200. 1600 ÷ 200 = 8 Interview ÷ 200 = 8 Interview every 8every 8thth kid. kid.

StratifiedStratified

Divide the population into groups Divide the population into groups (called strata) according to some (called strata) according to some characteristic that is important to the characteristic that is important to the study.study.

example: you might want to only example: you might want to only survey juniors.survey juniors.

ClusterCluster

Use an entire, intact, group.Use an entire, intact, group.

example: every person who example: every person who lives in a certain apartment building.lives in a certain apartment building.

example: every person in Mrs. example: every person in Mrs. Peddy’s third period class.Peddy’s third period class.

These are not the only methodsThese are not the only methods

convenience samplingconvenience sampling

- whatever is convenient to the - whatever is convenient to the researcher (Wal-mart)researcher (Wal-mart)

sequentialsequential double samplingdouble sampling multi-stagemulti-stage

Observational StudiesObservational Studies

The researcher merely observes The researcher merely observes what is happening or what has what is happening or what has happened in the past and tries to happened in the past and tries to draw conclusions based on these draw conclusions based on these observations.observations.

Experimental StudyExperimental Study

The researcher manipulates one of The researcher manipulates one of the variables and tries to determine the variables and tries to determine how the manipulation influences how the manipulation influences other variables.other variables.

teaching note: situpsteaching note: situps

In a true experimental study, In a true experimental study, subjects should be assigned subjects should be assigned randomlyrandomly

when random assignment is not when random assignment is not possible (i.e. existing classrooms), possible (i.e. existing classrooms), the study is said to be quasi-the study is said to be quasi-experimentalexperimental

Independent VariableIndependent Variable

The variable that is being The variable that is being manipulatedmanipulated

aka: explanatory variableaka: explanatory variable

Dependent VariableDependent Variable

The resultant variable.The resultant variable.

aka: outcome variable.aka: outcome variable.

When doing an experiment you When doing an experiment you generally need two groups:generally need two groups:

treatment group: the one you are treatment group: the one you are experimenting onexperimenting on

control group: the one you are doing control group: the one you are doing nothing to but observingnothing to but observing

Confounding VariableConfounding Variable

a variable that influences the a variable that influences the dependent or outcome variable but dependent or outcome variable but cannot by separated from the cannot by separated from the independent variable.independent variable.

Misuse of StatisticsMisuse of Statistics

3% of the students 3% of the students of Muskogee High of Muskogee High School want school School want school uniforms.uniforms. 64% of the 64% of the

students of students of Muskogee High Muskogee High School want school School want school uniforms.uniforms.

Which one is true?

The pure and simple truth is rarely pure and never simple

Oscar Wilde First get your facts; then you can distort

them at your leisureMark Twain

There are three kinds of lies: lies, damn lies, and statistics

Benjamin Disraeli

Three out of four doctors Three out of four doctors recommend new Zimentorecommend new Zimento

Suspect SamplesSuspect Samples

How many doctors were actually How many doctors were actually used?used?

4?4? 40?40? 100?100? 10,000?10,000? How were they chosen?How were they chosen?

Misleading GraphsMisleading Graphs

51% agree

49% disagree

Misleading wording in surveysMisleading wording in surveys

Do you support bringing freedom and Do you support bringing freedom and democracy to the people of Iraq?democracy to the people of Iraq?

Do you support the unprovoked Do you support the unprovoked military action of the U.S. taking military action of the U.S. taking place in Iraq?place in Iraq?

Changing values to represent the Changing values to represent the same datasame data

The incumbent states, “During my tenure The incumbent states, “During my tenure expenditures have only risen 1%.”expenditures have only risen 1%.”

The challenger states, “During my The challenger states, “During my opponents tenure expenditures have opponents tenure expenditures have risen $10,000,000.”risen $10,000,000.”

Both statements are true, but one uses Both statements are true, but one uses percentage and the other dollar amounts.percentage and the other dollar amounts.

Detached StatisticsDetached Statistics

Our brand of crackers has one-third Our brand of crackers has one-third fewer calories.fewer calories.

compared to what?compared to what?

Zimento works four times faster.Zimento works four times faster.

faster than what?faster than what?

Implied connectionsImplied connections

Eating fish may help to reduce your Eating fish may help to reduce your cholesterol.cholesterol.

Studies suggest that using Zimento Studies suggest that using Zimento will help you reduce your weight.will help you reduce your weight.

Taking calcium will lower blood Taking calcium will lower blood pressure in some people.pressure in some people.

AssignmentAssignment

Page 26Page 26

1 - 291 - 29