1.5 Bias in Sampling

What is a closed question?

A closed question has fixed choices for answers. Like multiple choice questions.

What is undercoverge in Sampling bias?

occurs when the proportion of one segment of the population is lower in a sample than it is in the population. Undercoverage can result if the frame used to obtain the sample is incomplete or not representative of the population.

What is open question?

An open question is a free-response question. These allow the respondents to state exactly how they feel, but are harder to analyze due to the variety of answers and possible misinterpretation of answers.

What can create response bias?

Interviewer error, Misrepresented Answers, wording of questions, type of questions (open or closed), data entry error,,

How can nonresponse bias be controlled?

Nonresponse bias can be controlled using callbacks. For example, if a mailed questionnaire was not returned, a callback might mean phoning the individual to conduct the survey. If an individual was not at home, a callback might mean returning to the home at other times in the day.

When does nonresponse bias exists?

Nonresponse bias exists when individuals selected to be in the sample who do not respond to the survey have different opinions from those who do.

A polling organization conducts a study to estimate the percentage of households that speaks a foreign language as the primary language. It mails a questionnaire to 1023 randomly selected households throughout the United States and asks the head of household if a foreign language is the primary language spoken in the home. Of the 1023 households selected, 12 responded. The survey has bias. (a) Determine the type of bias

Nonresponse bias; if the survey is only written in English, non-English speaking homes will not complete the survey, resulting in Undercoverage.

When does nonresponse bias occur?

Nonresponse can occur because individuals selected for the sample do not wish to respond or the interviewer was unable to contact them

What types of bias are considered nonsampling error?

Nonsampling errors result from undercoverage, nonresponse bias, response bias, or data-entry error. ***Nonsampling error is error that results from obtaining and recording the information collected.

An antigun advocate wants to estimate the percentage of people who favor stricter gun laws. He conducts a nationwide survey of 1203 randomly selected adults 18 years old and older. The interviewer asks the respondents, "Do you favor harsher penalties for individuals who sell guns illegally?" The survey has bias. (a) Determine the type of bias.

Response bias due to a poorly worded question.

When does response bias exist?

Response bias exists when the answers on a survey do not reflect the true feelings of the respondent.

What are the three sources of bias in sampling?

There are three sources of bias in sampling: 1.Sampling bias 2.Nonresponse bias 3.Response bias

The survey has bias. Determine the type of bias. A retail store manager wants to conduct a study regarding the shopping habits of his customers. He selects the first 60 customers who enter his store on a Saturday morning.

Sampling bias due to Undercoverage since the 1st 60 customers many not be representative of the population .

What is sampling bias mean?

Sampling bias means that the technique used to obtain the sample's individuals tends to favor one part of the population over another. Any convenience sample has sampling bias because the individuals are not chosen through a random sample.

Sampling error results from what?

Sampling error results from using a sample to estimate information about a population. This type of error occurs because a sample gives incomplete information about a population. ***We can think of sampling error as error that results from using a subset of the population to describe characteristics of the population.

What does bias mean in sampling?

The word bias could mean to give preference to selecting some individuals over others; it could also mean that certain responses are more likely to occur in the sample than in the population.

If the results of the sample are not representative of the population, then the sample has _________.

bias

What other methods can be used to improve nonresponse bias?

using rewards, such as cash payments for completing a questionnaire, or incentives such as a cover letter that states that the responses to the questionnaire will determine future policy.