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Sampling in research may be defined as:
a. insurance that each person has a chance of being included in the study.
b. establishment of criteria for eligibility to participate in a study.
c. identification of the population in which the researcher is interested.
d. selection of a subset of a population to represent the whole population.
Sampling involves selecting a group of people, events, behaviors, or other elements with which to conduct a study. Samples are expected to represent a population of people.
A researcher is interested in studying lifestyle management in patients with inflammatory bowel disease. The researcher contacts the Crohn's and Colitis Foundation of America to determine how to best access this patient population. Patients with inflammatory bowel disease are an example of which of the following?
a. Accessible population
d. Target population
The target population is the entire set of individuals who meet the sampling criteria.
Subjects who participate in a study of patients with inflammatory bowel disease are described as the:
a. accessible population.
d. target population.
A sample is that group of people who are representing the entire population and participating in the study. Samples are expected to represent an entire population.
The Crohn's and Colitis Foundation of America referred the interested researcher to a local chapter of the organization. The local chapter agreed to send out letters on behalf of the researcher inviting potential subjects to contact the researcher if they are willing to participate in a study. Potential subjects in this situation would be described as the:
a. accessible population.
d. target population.
An accessible population is the portion of the target population to which the researcher has reasonable access.
The population from which the researcher selects the actual study sample is referred to as the:
a. accessible population.
b. scientific population.
c. target population.
d. theoretical population.
An accessible population is the portion of the target population to which the researcher has reasonable access. The sample is obtained from the accessible population.
In a study of liver transplant recipients, the researcher specifies that the subjects must be 18 years of age or older and the recipient of only one liver transplant. These criteria are an example of:
a. demographic attributes.
b. exclusion criteria.
c. extraneous variables.
d. inclusion criteria.
Inclusion criteria are those characteristics that the subject or element must possess to be part of the target population.
The adequacy of a sample would be primarily based on which of the following criteria?
a. Method chosen for sample selection
b. Representativeness of the population
c. Size of the total population
d. Willingness of subjects to participate
A sample needs to be representative in terms of characteristics, such as age, gender, ethnicity, income, and education
A sample that accurately reflects the characteristics of the population from which it is drawn is a:
a. cluster sample.
b. purposive sample.
c. random sample.
d. representative sample.
Representativeness means that the sample, accessible population, and target population are alike in as many ways as possible.
Sample attrition would be reflected by the:
a. average death rate of the population under study.
b. inability to access identified members of a population.
c. number of patients who die while participating in a study.
d. number of patients who drop out of a study.
Sample attrition or mortality is the withdrawal or loss of subjects from a study
The term "comparison group" in research refers to the group of patients in a:
a. nonrandom sample who do not receive a treatment.
b. nonrandom sample who receive a treatment.
c. random sample who do not receive a treatment.
d. random sample who receive a treatment.
If nonrandom methods are used for sample selection, the group not receiving a treatment is referred to as a comparison group.
Which of the following would be the best method for randomly assigning subjects (n = 40) to treatment (n = 20) and control (n = 20) groups in an intervention study? Assign numbers to all subjects and:
a. ignore numbers; group the subjects by diagnosis or physician.
b. place the first 20 subjects in one group and the last in the other.
c. put even-numbered subjects in one group, odd numbered in the other.
d. put numbers 1 to 40 in a box and blindly draw from the box.
In the approach described, all 40 of the subjects have an equal chance of being assigned to either the treatment group or the control group.
Which of the following is true about probability sampling? Probability sampling:
a. can take different forms, but random selection is always used.
b. is the most economical way to get large numbers of subjects.
c. guarantees that the sample is representative.
d. subjects are handpicked because they have the expertise to provide information for the study.
Random sampling allows each individual in the population an opportunity to be selected for the sample.
Another name for probability sampling is:
a. accidental sampling.
b. purposive sampling.
c. quota sampling.
d. random sampling.
In probability sampling, every member of the population has a probability higher than zero of being selected for the sample. To achieve this probability, the sample is obtained randomly.
The researcher is to select a set of five subjects using a random numbers table. The selected population is 50. The researcher's pencil was initially placed on the second column from the left and third row down. The decision is to move across the columns to the right.
06 84 10 22 56 72 25 70 69 43
07 63 10 34 66 39 54 02 33 85
03 19 63 93 72 52 13 30 44 40
77 32 69 58 25 15 55 38 19 62
20 01 94 54 66 88 43 91 34 28
The subject numbers will be:
a. 13, 30, 44, 40, 32
b. 19, 38, 55, 15, 25
c. 19, 63, 93, 72, 52
d. 33, 02, 54, 39, 66
Which of the following statements is true about stratified random sampling?
a. Allows the researcher to use a smaller sample size
b. Ensures obtaining a larger sample at lower cost
c. Internal validity is strengthened with this type of sampling
d. Involves the selection of certain subjects from a convenience sample
With stratification, the researcher can use a smaller sample size and achieve the same degree of representativeness in relation to the stratified variable as a large sample acquired through simple random sampling.
Cluster sampling is:
a. a form of nonprobability sampling used in small surveys.
b. also known as multistage sampling.
c. unlikely to result in sampling errors.
d. useful when the target population is found in a small geographical area.
Both terms, cluster sampling and multistage sampling, have the same meaning in sampling methods.
A person is shopping in the mall and is approached by individuals who identify themselves as researchers for a local food chain. They ask the person to participate in their study by answering a few questions. As a subject for this survey, the person was selected by which method of sampling?
a. Convenience sampling
b. Purposive sampling
c. Random sampling
d. Systematic sampling
Findings of an intervention study with a convenience sample:
a. are generalizable to a wider group of patients with related problems.
b. are to be discounted because they are extremely biased.
c. provide no useful information.
d. should be replicated before being applied to a wider population.
Representativeness of the sample is a concern in convenience sampling, and generalizability is therefore limited.
Which type of sampling will get the largest number of subjects in the shortest period of time?
a. Cluster sampling
b. Convenience sampling
c. Network or snowball sampling
d. Random sampling
Which of the following types of sampling is considered to be the weakest?
Which of the following samples is least likely to be representative of the overall population?
d. Stratified random
An advantage of convenience sampling is:
a. ease in obtaining subjects.
b. increased internal validity and control.
c. low risk of sampling bias.
d. representativeness of sample is ensured.
Convenience samples are inexpensive, accessible, and usually require less time to acquire than other types of samples.
Which of the following study types would require the largest sample size?
c. Grounded theory
Descriptive studies and correlational studies often require very large samples. In these studies multiple variables may be examined, and extraneous variables are likely to affect subjects' responses to the variables under study.
The sample size needed for a study increases when:
a. the alpha level is increased from .01 to .05.
b. the number of variables in the study increases.
c. a one-tailed versus a two-tailed statistical test is used.
d. the sensitivity of the instruments used is high.
As the number of variables under study increases, the sample size needed may increase.
A researcher wants to obtain a sample of individuals who are HIV positive. Which of the following sampling methods would be the most effective way to obtain a sample?
a. Accidental sampling
b. Cluster sampling
c. Network sampling
d. Simple random sampling
Which of the following is true about network sampling?
a. Eligibility criteria do not need to be defined carefully.
b. Finding large numbers of subjects by this means is easy and economical.
c. Sample representativeness is guaranteed by using this technique.
d. Subjects who have knowledge of a situation, often sensitive or not socially acceptable, are identified by others in the same type of situation.
Network sampling is useful for locating samples difficult or impossible to obtain in other ways. Network sampling takes advantage of social networks and the fact that friends tend to have characteristics in common.
Which is the largest group from among this list?
a. Accessible population
b. Control group
d. Target population
The target population is the group the researcher wants to generalize to and needs the sample to represent.
Which of the following statements is true about sampling plans?
a. A probability sampling plan is a better plan than a nonprobability one.
b. A sampling plan outlines strategies used to obtain a sample for a study.
c. Each study has its own sampling method, unique to that project.
d. Getting a sample that is the most representative is the ideal, not the goal, of the sampling plan.
A sampling plan, or sampling method, defines the selection process for a study.
A researcher wanting to explore the lives of women newly diagnosed with breast cancer obtains a random sample of the population. What part of the study will be strengthened because of the random sample?
c. Statistical power
Random samples increase the validity of a study.
A researcher was able to obtain a list of all lung cancer patients in the Southeast. If a table of random numbers was used to create a sample from that original list and then those individuals agreed to participate in a study, what kind of sample would have been created?
c. Simple random
d. Stratified random
Simple random sampling is when every member of the population has an equal chance of selection for the sample.
In a study investigating nurses' attitudes toward taking care of respiratory disease patients who had a long history of smoking, the researcher randomly selected a sample from a list of all the registered nurses from a randomly selected list of four states in the Southeast. Because the sample was drawn randomly, to what population can the findings of the study be generalized? Registered nurses in the:
a. Selected four states
c. Southeast who are actively working
d. United States
This study used a cluster sampling technique that is one type of random sampling plan.
In a study investigating nurses' attitudes toward taking care of respiratory disease patients who had a long history of smoking, the researcher randomly selected a sample from a list of all the registered nurses from a randomly selected list of four states in the Southeast. If the researcher also selected the sample by randomly selecting nurses who smoke and those who do not, what sampling technique is being used?
c. Stratified random
Stratified random sampling is used when certain characteristics of the group are identified and then proportionately included in the randomly chosen sample. Assuming the researcher first knew whether or not a nurse smoked, then this represents that sampling technique.
Which of the following sets of terms represents an appropriate pairing of a probability sampling method and a corresponding nonprobability sampling one?
a. Cluster sampling—snowball technique
b. Simple random sampling—convenience sampling
c. Stratified random sampling—quota sampling
d. Theoretical sampling—quota sampling
Stratified random sampling and quota sampling both attempt to balance the sample in terms of known characteristics in the population.
Which of the following is true about sample size?
a. An adequate sample size is particularly important to detect differences when they do in fact exist.
b. Evaluating the possibility of a Type I error will help determine sample size.
c. Finding a significant difference in study groups occurs most often with smaller samples.
d. Sample size is especially important to support significant findings.
Evaluating the adequacy of the sample size is very important when no differences have been found. Too small a sample can result in no difference being detected, even when there actually is one.
A researcher reports on a study conducted to determine if a new educational program has helped dialysis patients become more compliant with their fluid restrictions. The findings indicated that there was no difference. The report did include that a power analysis was performed to determine if the sample size (n = 100) was adequate. The power level was .5. What should the reader conclude?
a. A sample of 100 is certainly adequate in a clinical study. The researcher should adjust the educational program.
b. Chances are high that a Type I error has occurred.
c. Findings of no difference are not surprising; it is difficult to make an impact on this population of patients.
d. There is a high likelihood that the sample size was not adequate, and the study should be replicated using more subjects.
A power level needs to reach .8 to be acceptable, and this one had only .5. There is a good chance that a Type II error occurred, and the study should be replicated.
Apart from sample size, which of the following is typically not considered when determining the power of a study?
a. Sensitivity of the instruments used
b. Number of variables
c. Skill of the researcher
d. Data analysis techniques
The skill of the researcher does not affect the statistical power of a study. All other answers are correct.
To detect a significant difference between two groups when the effect size is small, what should the researcher do?
a. Conduct a pilot study.
b. Obtain a different sample.
c. Increase the sample size.
d. Perform additional analysis.
Increasing the sample size makes it easier to detect a difference.
Which of the following types of studies would need the largest sample size?
a. Case studies
b. Descriptive studies
c. Experimental studies
d. Quasi-experimental studies
Descriptive studies often require very large samples. Multiple variables may be examined, and extraneous variables are likely to affect subject response(s) to the variables under study.
Why do qualitative researchers need to be as concerned with sample size as quantitative researchers do? Qualitative researchers:
a. are reaching the objectives of their study in a similar way.
b. need subjects who are able and willing to share their knowledge, oftentimes in repeated and more in-depth interviews than subjects in quantitative studies.
c. need to gain a narrow focus rather than a broad perspective as their research purpose.
d. will be analyzing the data with statistical techniques that require certain numbers of subjects.
Qualitative research oftentimes requires the subjects to share their knowledge of the topic being studied in an in-depth level in repeated interviews. Therefore the researcher needs to ensure that the sample size is adequate to provide the depth and rich data that are required.
Which of the following is an example of purposive sampling?
a. The names of all possible subjects are put into a hat, and an adequate number are drawn out.
b. Volunteers are solicited from the entire population, and those who agree become subjects in the study.
c. Sample members are determined by finding a designated number of subjects from each of several identified groups (men, women, high school graduates, etc.).
d. Subjects who have knowledge about the study topic are asked to participate in the study; those who agree become the sample.
Purposive sampling is when appropriate subjects are found by the researcher and asked to participate in the study.
Which of the following are not correctly paired as similar types of sampling methods?
a. Convenience sampling—accidental sampling
b. Network sampling—snowball sampling
c. Purposive sampling—selective sampling
d. Stratified random sampling—quota sampling
Stratified random sampling and quota sampling differ in randomness; quota sampling does not allow for equal likelihood of entering the sample from the target population.
Convenience and accidental sampling describe similar types of sampling methods.
Which of the following is true about theoretical sampling?
a. All studies use theoretical sampling as a background for creating the sample.
b. Grounded theory research frequently uses theoretical sampling to develop a selected theory.
c. Subjects are selected to participate in a research study to match certain theory characteristics.
d. Theoretical sampling is a little-used, but powerful method of creating a sample for quantitative research.
Because of the nature of grounded theory methodology, theoretical sampling is used.
Which of the following is true about sample size in a qualitative study?
a. "Adequate sample size" is of no concern to a qualitative researcher because there is no statistical analysis involved.
b. Sample size is deemed to be adequate when the researcher is detecting no new knowledge from additional subjects.
c. Subjects who have knowledge of a situation assist the researcher in determining whether the sample size is adequate.
d. There is a test similar to the power analysis in a quantitative study that can be used to determine an adequate sample size for qualitative research.
In qualitative research, the researcher looks for data saturation, which is reached when no new information is being discovered from additional subjects.
Which of the following factors do not influence saturation of data and therefore sample size in a qualitative study?
a. Quality of the data
b. Randomization of the sample
c. Scope of the study
d. Study design
Randomization of the data is a concern for quantitative research designs. All other choices are concerns for saturation of data in qualitative research.
Which of the following research settings is not correctly paired with the type of setting?
a. Clinical research unit—highly controlled setting
b. Indoor playroom—natural setting
c. Primary care clinic—partially controlled setting
d. Subject's home—partially controlled setting
A subject's home would be a natural research setting, so it is paired incorrectly with "partially controlled setting."
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