13. what sampling method is used in the follo...
13. what sampling method is used in the following examples? is the method biased or not? see example 3\na. a clothing manufacturing company divided its employees up by units, and then they randomly selected three employees from each unit to represent the company at a convention in las vegas.\nb. mr.yotsey put names of all students at his school on identical slips of paper in a box and distributed surveys to the students whose names he pulled.\n14. researchers want to find out if warm water therapy increases muscle strength in people 65 years of age and older. describe a design for a controlled study of this question. what are some potential sources of bias in your study? see example 4
Answer
# Brief Explanations:
## 13a.
The sampling method is stratified sampling as the population (employees) is divided into units (strata) and samples are selected from each stratum. It may be biased if the units are not homogeneous and the selection of three employees per unit does not accurately represent the whole company's characteristics.
## 13b.
This is simple random sampling as each student has an equal chance of being selected. It is unbiased as long as the selection process is truly random and there are no external factors influencing which names are pulled.
## 14.
**Study Design**:
- Divide the population of people 65 years of age and older into two groups: a treatment group that receives warm - water therapy and a control group that does not.
- Measure the muscle strength of all participants at the start of the study (pre - test).
- Have the treatment group undergo the warm - water therapy for a set period, while the control group does not receive any such therapy.
- Measure the muscle strength of all participants again at the end of the study (post - test).
- Compare the changes in muscle strength between the two groups.
**Potential Sources of Bias**:
- Self - selection bias: If participants choose whether to be in the treatment or control group, those with more motivation or better initial health may be more likely to choose the treatment group.
- Experimenter bias: The researchers may unconsciously treat the two groups differently or interpret the results in a way that supports their hypothesis.
- Placebo effect: Participants in the treatment group may believe the warm - water therapy will work and show improvement due to this belief rather than the actual therapy.
# Answer:
## 13a.
Sampling method: Stratified sampling. Biased: Potentially.
## 13b.
Sampling method: Simple random sampling. Biased: No.
## 14.
Study design: Divide into treatment and control groups, pre - test and post - test muscle strength. Potential sources of bias: Self - selection bias, experimenter bias, placebo effect.