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Ch. 1 - Introduction to Statistics
Larson - Elementary Statistics: Picturing the World 8th Edition
Larson8th EditionElementary Statistics: Picturing the WorldISBN: 9780137493470Not the one you use?Change textbook
All textbooksLarson 8th EditionCh. 1 - Introduction to StatisticsProblem 1.r.24
Chapter 1, Problem 1.r.24

Identify the sampling technique used, and discuss potential sources of bias (if any). Explain.
A student asks 18 friends to participate in a psychology experiment.

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Identify the sampling technique: The student is selecting participants based on convenience, as they are asking their friends. This is an example of a convenience sampling technique.
Explain convenience sampling: Convenience sampling involves selecting individuals who are easiest to reach or readily available. It is not random and does not ensure that every individual in the population has an equal chance of being selected.
Discuss potential sources of bias: Since the sample consists only of the student’s friends, it is not representative of the broader population. This introduces selection bias, as the sample may share similar characteristics (e.g., age, interests, or social background) that do not reflect the diversity of the entire population.
Explain the impact of bias: The lack of representativeness can lead to results that are not generalizable to the entire population. For example, conclusions drawn from this experiment may only apply to the student’s social circle and not to other groups.
Suggest improvements: To reduce bias, the student could use a random sampling technique, such as simple random sampling, where participants are chosen randomly from the entire population of interest. This would increase the likelihood of obtaining a representative sample.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Sampling Technique

Sampling technique refers to the method used to select individuals from a population to participate in a study. In this case, the student is using a non-probability sampling technique known as convenience sampling, as they are selecting friends who are readily available rather than randomly selecting from the entire population.
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Sampling Distribution of Sample Proportion

Bias in Sampling

Bias in sampling occurs when certain members of a population are systematically more likely to be selected than others, leading to results that may not be representative. In this scenario, the potential bias arises from the fact that the sample consists only of friends, which may not reflect the broader population's diversity in terms of demographics, opinions, or behaviors.
Recommended video:
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Sampling Distribution of Sample Proportion

Generalizability

Generalizability refers to the extent to which findings from a sample can be applied to the larger population. Due to the convenience sampling method and potential biases, the results of the psychology experiment may lack generalizability, making it difficult to draw conclusions that apply to individuals outside of the student's friend group.
Related Practice
Textbook Question

"Researchers in Japan tested the effect of cannabidiol (CBD) in treating late teenagers with social anxiety disorder (SAD). Thirty-seven 18- to 19-year-old teenagers with SAD took part in the study. The patients were assigned at random to receive a daily dose of either CBD or a placebo for 4 weeks. Symptoms were measured using The Fear of Negative Evaluation Questionnaire and the Liebowitz Social Anxiety Scale at the beginning and end of the treatment. (Source: Frontiers in Psychology)

The experiment is described as a placebo-controlled, double-blind study. Explain what this means."

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Textbook Question

200 students volunteer for an experiment to test the effects of sleep deprivation on memory recall. The students will be placed in one of five different treatment groups, including the control group.

Explain how you could design an experiment so that it uses a completely randomized design.

207
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Textbook Question

"Researchers in Japan tested the effect of cannabidiol (CBD) in treating late teenagers with social anxiety disorder (SAD). Thirty-seven 18- to 19-year-old teenagers with SAD took part in the study. The patients were assigned at random to receive a daily dose of either CBD or a placebo for 4 weeks. Symptoms were measured using The Fear of Negative Evaluation Questionnaire and the Liebowitz Social Anxiety Scale at the beginning and end of the treatment. (Source: Frontiers in Psychology)

How could blocking be used in designing this experiment?"

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Textbook Question

A company wants to test the effectiveness of a new acne cream. The company recruits 500 girls ages 13 to 17 who have acne. The subjects are randomly assigned into two groups. One group is given the acne cream and the other is given a placebo that looks exactly like the acne cream. Both groups apply the cream daily for two months. Facial photos are taken at the beginning and end of the treatment to compare results.

c. How could this experiment be designed to be double-blind?

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Textbook Question

Determine whether the study is an observational study or an experiment. Explain.

Researchers conduct a study to determine whether a medication based on fish oil known as omega-3 carboxylic acids is effective in reducing the risk of cardiac events in people already at risk. In the study, 13,078 patients are randomly chosen to receive either omega-3 carboxylic acids or a placebo of corn oil daily. Researchers compare the number of cardiac events of the two groups over similar follow-up periods of time. (Source: American Heart Association)

180
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Textbook Question

200 students volunteer for an experiment to test the effects of sleep deprivation on memory recall. The students will be placed in one of five different treatment groups, including the control group.

Explain how you could design an experiment so that it uses a randomized block design.

166
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