stat 1.3
Determine whether the statement is true or false. If it is false, rewrite it as a true statement. Using a systematic sample guarantees that members of each group within a population will be sampled.
False. Using a stratified sample guarantees that members of each group within a population will be sampled.
What technology format could be used to generate twelve random numbers between 1 and 750?
RandInt(1,750,12)
What is the difference between a census and a sampling?
A census includes the entire population. A sampling includes only part of the population.
Two types of survey questions are open questions and closed questions. An open question allows for any kind of response; a closed question allows for only a fixed response. An open question and a closed question with its possible choices are given below. List the advantages and disadvantages of each question. Open question: What can be done to get students to eat healthier foods? Closed question: How would you get students to eat healthier foods? 1. Mandatory nutrition course 2. Offer only healthy foods in the cafeteria and remove unhealthy foods 3. Offer more healthy foods in the cafeteria and raise the prices on unhealthy foods
(- An open question allows for new solutions to be introduced. & - An open question allows the respondent to go in-depth with their answer.) (- It is difficult to quantify the responses of open questions. - The form of the question may influence the opinion of the respondent - It is difficult to compare the results of surveys with open questions.) (- It is easy to quantify and compare the results of surveys with closed questions - It is possible to automate the collection of results for closed questions.) (- The form of the question may influence the opinion of the respondent. - Closed questions may not provide appropriate alternative responses.)
Use the row of numbers shown below to generate 12 random numbers between 01 and 99. 79012 08168 50961 54503 28043 50955 36294 Starting at the beginning of the row, what are the first 12 numbers between 01 and 99 in the sample?
- 79, 01, 20, .... until you get eleven numbers
A pharmaceutical company wants to test the effectiveness of a new allergy drug. The company identifies 250 females 30-35 years old who suffer from severe allergies. The subjects are randomly assigned into two groups. One group is given the new allergy drug and the other is given a placebo that looks exactly like the new allergy drug. After six months, the subjects' symptoms are studied and compared. Answer parts (a) through (c) below.
- The experimental units are the 30- to 35-year-old females being given the treatment. The treatment is the new allergy drug. -There may be a bias on the part of the researcher if the researcher knows which patients were given the real drug. -The study would be a double-blind study if both the researcher and the patient did not know which patient received the real drug or the placebo.
Why is drinking soda bad for you?
- The question is biased. The wording "How do you think drinking soda affects your health?" would be better.
The most popular house color among the 50 employees of a company
- The study is a census, because the population is small enough for it to be practical to record all of the responses.
The average weight of 75,000 online movie rental subscribers
- The study would use a sampling. The study would use simple random sampling because it would be easy for the company to randomly select a portion of its subscribers
A company has been rating television programs for more than 60 years. It uses several sampling procedures, but its main one is to track the viewing patterns of 20,000 households. These contain more than 45,000 people and are chosen to form a cross section of the overall population. The households represent various locations, ethnic groups, and income brackets. The data gathered from the sample of 20,000 households are used to draw inferences about the population of all households in the United States. Complete parts (a) and (b) below.
- The various locations, ethnic groups, and income brackets that are represented - Stratified sampling ensures that each segment of the population is represented.
How often do you eat cake during an average month?
- No, because it does not lead the respondent to any particular answer.
After a tornado, a disaster area is divided into 200 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.
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 (- 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)
Questioning students as they leave a university library, a researcher asks 330 students about their drinking habits.
Convenience sampling is used, because students are chosen due to convenience of location. (- 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)
Determine whether the statement is true or false. If it is false, rewrite it as a true statement. The method for selecting a stratified sample is to order a population in some way and then select members of the population at regular intervals.
False. The method for selecting a systematic sample is to order a population in some way and then select members of the population at regular intervals.
Observational studies are sometimes referred to as natural experiments. Explain what this means.
In an observational study, a researcher measures characteristics of interest of a part of a population but does not change existing conditions.
What is the difference between an observational study and an experiment?
In an experiment, a treatment is applied to part of a population and responses are observed. In an observational study, a researcher measures characteristics of interest of a part of a population but does not change existing conditions.
What is replication in an experiment? Why is replication important?
Replication is repetition of an experiment under the same or similar conditions. Replication is important because it enhances the validity of the results.
Chosen at random, 490 customers at a department store are contacted and asked their opinions of the service they received.
Simple random sampling is used, since the business is selecting from its customers at random, and all samples of 490 customers have an equal chance of being selected -The wording of the question asked to the customers may influence them towards a particular response. The results would not be usable in this case.
In 1965, researchers used random digit dialing to call 1200 people and ask what obstacles kept them from buying insurance.
Simple random sampling was used, since each number had an equal chance of being dialed, so all samples of 1200 phone numbers had an equal chance of being selected. (-Individuals may have not been available when the researchers were calling. Those individuals that were available may have not been representative of the population. -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 refused to participate in the sample. This may have made the sample less representative of the population.)
Wheat is planted on a 50-acre field. The field is divided intoone-acre subplots. A sample is taken from each subplot to estimate the harvest.
Stratified sampling is used, since the field is divided into subplots and a random sample is taken from each subplot. - Certain subplots may have more or fewer wheat plants than others. Samples from these subplots may bias the overall sample.
Every sixteenth person entering a mall is asked to choose his or her favorite store from a list of five different stores that includes a description of each. What type of sampling is used?
Systematic sampling is used, because every sixteenth person is selected (- If there is a regular pattern to the people entering the mall, the sample may not be representative. -The wording of the question may direct respondents towards a particular store.)
Determine whether the following statement is true or false. If it is false, rewrite it as a true statement. A placebo is an actual treatment.
The statement is false. A placebo is a fake treatment.
Determine whether the following statement is true or false. If it is false, rewrite it as a true statement. A double-blind experiment is used to increase the placebo effect.
The statement is false. Double blinding is used to decrease the placebo effect.
Determine whether the study is an observational study or an experiment. Explain. To study the effects of social media on teenagers' brains, researchers showed a few dozen teenagers photographs that had varying numbers of "likes" while scanning the reactions in their brains.
The study is an experiment, because it applies a treatment to the teenagers.
Determine whether the study is an observational study or an experiment. Explain. In a survey of 1356 adults in a country, 53% said the country's leader should release all medical information that might affect their ability to serve.
The study is observational, because it does not apply a treatment to the adults
What is the difference between a random sample and a simple random sample?
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.