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What is random sampling? Why is it used and how does it compare with convenience sampling?

Short Answer

Expert verified
Random sampling ensures each member of the population has an equal chance of selection to eliminate biases, unlike convenience sampling, which is easier but may introduce biases and not accurately represent the population.

Step by step solution

01

- Definition of Random Sampling

Random sampling is a technique where each member of the population has an equal chance of being selected. This method minimizes biases and ensures that the sample represents the entire population.
02

- Purpose of Random Sampling

Random sampling is used to obtain a sample that fairly represents the population so that the results of the study can be generalized to the entire population. It is particularly useful in statistical analysis and helps in eliminating selection bias.
03

- Definition of Convenience Sampling

Convenience sampling is a technique where the sample is taken from a group that is conveniently accessible to the researcher. This method does not give each member of the population an equal chance of being selected.
04

- Comparison between Random Sampling and Convenience Sampling

Random sampling is more generalizable and eliminates selection bias, whereas convenience sampling is easier and less costly but may introduce significant biases and may not represent the population accurately. Random sampling is preferable for scientific studies to ensure validity, while convenience sampling might be used for preliminary research or when resources are limited.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Understanding Convenience Sampling
Convenience sampling is a method where the researcher selects a sample based on ease of access. For example, surveying people at a nearby shopping mall. This method, although easy and quick, has drawbacks. One major issue is that it does not provide each member of the population an equal chance of being selected.
This can result in selection bias, where certain groups are overrepresented or underrepresented, affecting the accuracy of the study. While convenient, this approach often compromises the quality and generalizability of the results.
Convenience sampling is often used in preliminary research where resources are limited, but it's important to be aware of its limitations. By understanding these pitfalls, researchers and students can better appreciate why more rigorous methods like random sampling are usually preferred for scientific studies.
The Problems of Selection Bias
Selection bias occurs when certain members of a population are more likely to be included in a sample than others. This can lead to inaccurate results. In random sampling, every member of the population has an equal chance of being selected, minimizing selection bias.
However, in convenience sampling, selection bias is a common issue. For instance, choosing a sample from a specific location might exclude people who do not visit that place. These exclusionary practices can skew the data, making it difficult to generalize the findings to the entire population.
Recognizing and mitigating selection bias is crucial for reliable statistical analysis. Researchers should strive to use sampling methods that minimize this bias to ensure their results are valid and applicable on a broader scale.
The Role of Statistical Analysis
Statistical analysis plays a critical role in interpreting data collected from samples. Once data is gathered, statistical tools and methods help in making sense of the data, drawing conclusions, and making predictions.
Random sampling is essential for the accuracy of statistical analysis because it ensures that the sample represents the population correctly. This representation allows researchers to generalize their findings with greater confidence. On the other hand, convenience sampling can compromise data quality, making statistical analysis less reliable.
Understanding the differences between sampling methods can help improve the integrity of statistical analysis. Employing random sampling techniques can lead to more valid results, which are crucial for evidence-based decisions and scientific advancements.

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Most popular questions from this chapter

Researchers wanted to determine whether the stomach shrinks as a result of dieting. To do this, they randomly divided 23 obese patients into two groups. The 14 individuals in the experimental group were placed on a diet that allowed them to consume 2508 kilojoules \((\mathrm{kJ})\) per day for 4 weeks. The 9 subjects in the control group ate as they normally would. To assess the size of the stomach, a latex gastric balloon was inserted into each subject's stomach and filled with the maximum amount of water that could be tolerated by the patient. The volume of water was compared to the volume that could be tolerated at the beginning of the study. The experimental subjects experienced a \(27 \%\) reduction in gastric capacity, while the subjects in the control group experienced no change in gastric capacity. It was concluded that a reduction in gastric capacity occurs after a restricted diet. (a) What type of experimental design is this? (b) What is the population that the results of this experiment apply to? (c) What is the response variable in this study? Is it qualitative or quantitative? (d) What are the treatments? (e) Identify the experimental units. (f) Draw a diagram similar to Figure \(7,8,\) or 10 to illustrate the design.

A research objective is presented. For each, identify the population and sample in the study. Folate and Hypertension Researchers want to determine whether or not higher folate intake is associated with a lower risk of hypertension (high blood pressure) in women ( 27 to 44 years of age). To make this determination, they look at 7373 cases of hypertension in these women and find that those who consume at least 1000 micrograms per day \((\mu \mathrm{g} / \mathrm{d})\) of total folate had a decreased risk of hypertension compared with those who consume less than \(200 \mu \mathrm{g} / \mathrm{d}\).

You wonder whether green tea lowers cholesterol. (a) To research the claim that green tea lowers LDL (so-called bad) cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels. Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the non-green tea drinkers. Explain why this is an observational study. (b) Name some lurking variables that might exist in the study (c) Suppose, instead of surveying individuals regarding their tea-drinking habits, you decide to conduct a designed experiment. You identify 120 volunteers to participate in the study and decided on three levels of the treatment: a placebo, one cup of green tea daily, two cups of green tea daily. The experiment is to run for one year. The response variable will be the change in LDL cholesterol for each subject from the beginning of the study to the end. What type of experimental design is this? (d) Explain how you would use blinding in this experiment. (e) What is the factor? Is it qualitative or quantitative? (f) What factors might you attempt to control in this experiment. (g) Explain how to use randomization in this experiment. How does randomization neutralize those variables that are not controlled? (h) Suppose you assigned 40 subjects to each of the three treatment groups. In addition, you decided to control the variable exercise by having each subject perform 150 minutes of cardiovascular exercise each week by walking on a treadmill. However, the 40 subjects in the placebo group decided they did not want to walk on the treadmill and skipped the weekly exercise. Explain how exercise is now a confounding variable.

Discuss a possible advantage of offering rewards or incentives to increase response rates. Are there any disadvantages?

What is the role of randomization in a designed experiment? If you were conducting a completely randomized design with three treatments and 90 experimental units, describe how you would randomly assign the experimental units to the treatments.

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