statistic 1.3: data collection and experimental design

Simple random sampling was​ used, since each number had an equal chance of being​ dialed, so all samples of 1000 phone numbers had an equal chance of being selected.

identify the sampling techniques: In 1965, reseachers used random digits dialing to call 1,000 people and ask what obstacles kept them from attending sporting events.

​No, because it does not lead the respondent to any particular answer.

is the statement bias? How often do you eat fast food during an average month​?

yes

is the statement bias? Why is walking every day good for​ you?

The given description corresponds to an experiment

obervational study or experiment? in a study of 436 men with a particular disease, the subjects were injected with vitamins to determine if the vitamins have an effect on the disease.

observational study

observational study or experiment?Research is conducted to determine if there is a relation between skin cancer and hair color.

The statement is false. A placebo is a fake treatment.

true/false? A placebo is an actual treatment.

False. Using a stratified sample guarantees that members of each group within a population will be sampled.

true/false? Using a systematic sample guarantees that members of each group within a population will be sampled.

Because of the personal nature of the​ question, students may not answer honestly. The sample only consists of members of the population that are easy to get. These members may not be representative of the population.

what potential sources of bias are present if any? Questioning students as they leave a university library​, a researcher asks 377 students about their eating habits.

Telephone sampling only includes people who had telephones. People who owned telephones may have been older or wealthier on​ average, and may not have been representative of the entire population. Individuals may have not been available when the researchers were calling. Those individuals that were available may have not been representative of the population. Individuals may have refused to participate in the sample. This may have made the sample less representative of the population.

what potential sources of bias were present, if any? In 1965, reseachers used random digits dialing to call 1,000 people and ask what obstacles kept them from attending sporting events.

Convenience sampling is​ used, because students are chosen due to convenience of location.

what type of sampling is used: Questioning students as they leave a university library​, a researcher asks 377 students about their eating habits.

Replication is repetition of an experiment under the same or similar conditions. Replication is important because it enhances the validity of the results.

What is replication in an​ experiment? Why is replication​ important?

A census includes the entire population. A sampling includes only part of the population

What is the difference between a census and a​ sampling?

With a random​ sample, each individual has the same chance of being selected. With a simple random​ sample, all samples of the same size have the same chance of being selected.

What is the difference between a random sample and a simple random​ sample?

Certain grids may have been much more severely damaged than others. Severely damaged grids may have fewer occupied households. Certain grids may have been much more severely damaged than others. The grids that are selected may not be representative in terms of damage.

What potential sources of bias are​ present, if​ any?

Certain subplots may have more or fewer carrot plants than others. Samples from these subplots may bias the overall sample

What potential sources of bias are​ present, if​ any? Carrots are planted on a 44-acre field. The field is divided into one-acre subplots. A sample is taken from each subplot to estimate the harvest.

The wording of the question may direct respondents towards a particular author If there is a regular pattern to the people entering the library​, the sample may not be representative.

What potential sources of bias are​ present, if​ any? Every thirteenth person entering a library is asked to choose his or her favorite author from a list of five different authors that includes a description of each.

Cluster sampling is​ used, since the disaster area is divided into​ grids, and some of those grids are selected and everyone in those grids is interviewed.

What type of sampling is​ used? After a flood​, a disaster area is divided into 150 equal grids. Thirty of the grids are​ selected, and every occupied household in the grid is interviewed to help focus relief efforts on what residents require the most.

Stratified sampling is​ used, since the field is divided into subplots and a random sample is taken from each subplot.

What type of sampling is​ used? Carrots are planted on a 44-acre field. The field is divided into one-acre subplots. A sample is taken from each subplot to estimate the harvest.

Systematic sampling is​ used, because every thirteenth person is selected

What type of sampling is​ used? Every thirteenth person entering a library is asked to choose his or her favorite author from a list of five different authors that includes a description of each.

sampling

Would you take a census or use a​ sampling? The average credit card debt of the 20,000 employees of a company

The original question is not biased.

correct the statement to not make it bias, if needed: How often do you eat fast food during an average month​?

How do you think walking every day affects your​ health?

correct the statement to not make it bias, if needed: Why is walking every day good for​ you?