1.5 bias in sampling

(a) determine the type of bias (b) suggest a remedy an antigum advocate wants to estimate the % of people who favor stricter gun laws. He conducts a nationwide survey of 1203 randomly selected adults 18 and older. the interviewer asks the respondents, "Do you favor harsher penalties for individuals who sell guns illegally."?

(a) Response bias, due to poorly worded question. (b) rewrite the question. Add words such as "Approve and disapprove" Example: Do you approve or disapprove of harsher penalties for individuals who sell gun illegally?

(a) determine the type of bias (b) suggest a remedy a polling organization conducts a study to estimate the % 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.

(a) non-response bias: non english speaking homes will not complete the survey, resulting in undercoverage. (b) face to face, or telephone interviews.

(a) Determine the type of Bias (b) suggest a remedy 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.

(a) sampling bias, due to undercoverage. (b) systematic random sampling

what are the 3 sources of bias in sampling?

1.Sample bias 2. nonresponse bias 3.response bias

in what ways can response bias occur?

1.interview error 2.misinterpreted answers 3.wording of questions 4.ordering of questions 5.type of question. 6.data-entry error.

Many polls use random digit dialing to obtain a sample, which means a computer randomly generates phone numbers of landlines and cellphones. What is the frame for this type of sampling? who would be excluded from the survey and how might this affect the results of the survey?

Frame would be anyone with phone. The people without a phone and the homeless would be excluded. This can result in undercoverage.

what is undercoverage?

Undercoverage occurs when some individuals/groups in the population are left out of the process of choosing the sample. This means that some individuals/groups are not in the sampling frame.

what is nonresponse bias?

When people do not respond to surveys or answer the phone, the experiment will suffer.

what does it mean when a part of the population is under represented?

a certain segment of the population is lower in a sample than it is in the population.

What is a closed question? what is an open question? Discuss the advantages and disadvantages of each type.

a closed question has fixed choices for answers, open question is a free response question. Advantages: closed questions are easier to answer and open questions give more variety. Disadvantages: closed questions limit responses and open questions are hard to analyze due to the variety of answers.

Surveys tend to suffer from low response rates. based on past experience a researcher determines that the typical response rate for an email survey is 40%. She wishes to obtain a sample of 300 respondents so she emails the survey to 1500 randomly selected email addresses. Assuming the response rate for her survey is 40% will the respondents form an unbiased sample? explain.

no, the survey still suffers from undercoverage, non response bias and potentially response bias.

distinguish between nonsampling error and sampling error.

nonsampling error: The error that results from undercoverage, nonresponse bias, response bias or data-entry. it is the error that comes from the process of obtaining the data. Sampling error: results from using a sample to estimate information about a population.

what is sampling bias?

the technique used to obtain the sample's individuals tends to favor one part of the population over another. results are due to undercoverage

what is response bias?

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