Ch. 1 - Intro to Statistics

Population

the entire group of objects in our study

Sample

part of a population

Measurements on populations are called…

parameters

Measurements on samples are called…

statistics

Unit / experimental unit

what we are collecting data on (a singular person, event, thing, etc.)

Variable

a property of a unit we wish to measure

(can be classified as qualitative or quantitative)

Qualitative variable

classifies units into categories; can be observed, not measured numerically

ex. eye color

Quantitative variable

numerical values or counts; can be put into math operations

ex. height and weight

A quantitative variable is discrete when…

it involves limited or exclusively whole numbers

A quantitative variable is continuous when…

it can take on any value in an interval, including decimals

According to the Campus Housing Fact Sheet at a Big-Ten University, 60% of the students living in campus housing are in-state residents. In a sample of 200 students living in campus housing, 56.5% were found to be in-state residents.

In this situation, the value of 60% is a…

A. parameter

B. statistic

parameter

According to the Campus Housing Fact Sheet at a Big-Ten University, 60% of the students living in campus housing are in-state residents. In a sample of 200 students living in campus housing, 56.5% were found to be in-state residents.

In this situation, the value of 56.5% is a…

A. parameter

B. statistic

statistic

A census asks every household in a city how many children under the age of 18 reside there.

Parameter or statistic?

Qualitative, discrete (quantitative), or continuous (quantitative)?

Parameter

Quantitative (continuous)

A runner records the distance he runs each day.

Qualitative, discrete (quantitative), or continuous (quantitative)?

Quantitative (continuous)

A census asks residents for the highest level of education they have obtained: less than high school, high school, 2-year degree, 4-year degree, master’s degree, doctoral/professional degree.

Qualitative, discrete (quantitative), or continuous (quantitative)?

Quantitative (discrete)

Which method of data collection would you use to collect data for this study: the effect of changing flight patterns on the number of airplane accidents.

A. observational study

B. perform an experiment

C. use a simulation

D. administer a survey

use a simulation

Which method of data collection would you use to collect data for this study: the effect of eating oatmeal on lowering blood pressure.

A. observational study

B. perform an experiment

C. use a simulation

D. administer a survey

perform an experiment

Which method of data collection would you use to collect data for this study: how fourth graders solve a puzzle.

A. observational study

B. perform an experiment

C. use a simulation

D. administer a survey

observational study

Which method of data collection would you use to collect data for this study: U.S. residents’ approval rating of the U.S. president.

A. observational study

B. perform an experiment

C. use a simulation

D. administer a survey

administer a survey

Census

a count or measure of an entire population

• often expensive and difficult to perform

Sampling

a count or measure of part of a population

• most commonly used in statistics

Simple random sample

every sample (of the same size) is equally likely to be picked

• most common

Stratified sample

members of the population are divided into 2+ groups (strata) that share a common characteristic, and then an equal number of samples is randomly selected from each group

Cluster sample

divide the population into 2+ groups (clusters), select one or more, and sample everyone in the chosen group

• occurs when the population is already divided into naturally occurring subgroups

Systematic sample

every member of the population is assigned a number, and samples are pulled at intervals from the starting number

Identify the sampling technique.

Every tenth person entering a mall is asked to name his or her favorite basketball player.

A. simple random

B. stratified

C. cluster

D. systematic

systematic

Identify the sampling technique.

Using random digit dialing, researchers call 1400 people and ask what obstacles (such as childcare) keep them from exercising.

A. simple random

B. stratified

C. cluster

D. systematic

simple random

Identify the sampling technique.

After a hurricane, a disaster area is divided into 200 equal grids. Thirty of the grids are randomly selected, and every occupied household in the grid is interviewed to help focus relief efforts on what residents require the most.

A. simple random

B. stratified

C. cluster

D. systematic

cluster

Identify the sampling technique.

Chosen at random, 500 rural and 500 urban persons age 65 or older are asked about their health and their experience with prescription drugs.

A. simple random

B. stratified

C. cluster

D. systematic

stratified

Bias

the systematic favoring of certain outcomes

Sampling / systematic bias

systematic favoring of certain outcomes due to the methods employed to obtain the sample

Non-response bias

a type of systematic (sampling) bias where certain outcomes are favored when the individuals who choose to participate in a study differ from the individuals who choose to not participate

Response bias

a type of systematic (sampling) bias where certain outcomes are favored when participants do not respond truthfully (possibly to align with social norms or to appease the researcher)

Classify as response bias or non-response bias.

Retail Store Hours: A retail store was considering expanding their operating hours. To determine if this was a need perceived by their customers, they conducted a survey over the telephone to obtain data. Research assistants called the phone numbers of customers who were randomly selected to participate between the hours of 9AM and 4PM. Individuals who were at work were less likely to answer their phone call or agree to participate in the study than individuals who were at home at that time.

Non-response bias

Classify as response bias or non-response bias.

Using an anonymous online survey, a professor asks his students: have you cheated on an exam in my class? Many of the students who have cheated still answered no.

Response bias