Diagnose the statistical and design error in the researcher's study. Explain why her conclusion is misleading by referencing the correlation values expected across both the restricted group and the general population, and explain how she can correct her study's design.
Case context: A researcher conducts a study on the relationship between age and the enjoyment of hip hop music. Due to convenience, she only recruits participants from a local college campus who are between the ages of and . After analyzing the data, she finds a Pearson's of and publishes a paper concluding that age has no relationship to hip hop music enjoyment.
Question: Diagnose the statistical and design error in the researcher's study. Explain why her conclusion is misleading by referencing the correlation values expected across both the restricted group and the general population, and explain how she can correct her study's design.
Sample answer: The researcher committed the error of restriction of range by only sampling - to -year-olds. This restriction caused the correlation to drop to , making the relationship appear artificially weak. Across the general population, there is actually a strong negative correlation of . To correct this design, she must sample a wide range of values (ages) to capture the overall trend accurately.
Key points:
- Identify the issue as a restriction of range due to only sampling - to -year-olds.
- Explain that range restriction obscures the relationship, dropping the correlation to .
- Contrast the restricted result with the general population's correlation of .
- Propose correcting the design by sampling a wider range of age values.
Rubric: Grades should be based on: 1. Identifying the design error as restriction of range (3 points). 2. Contrasting the restricted sample correlation () with the general population correlation () (4 points). 3. Explaining the correction of sampling a wider range of values/ages (3 points).
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Research Methods in Psychology - 4th American Edition @ KPU
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When studying the relationship between age and enjoyment of hip hop music, what happens to the observed correlation if data is collected exclusively from a narrow age group, such as 18- to 24-year-olds?
True or False: In the study of age and hip-hop enjoyment, the correlation coefficient drops from -0.77 to zero when the sample is restricted to 18- to 24-year-olds because there is no longer enough variation in the age variable to reveal the broader trend.
A researcher is investigating how age relates to the enjoyment of hip hop music. Based on the provided scatterplots and the principle of range restriction, match each sampling scenario or concept with its corresponding statistical outcome.
Examine the scatterplots provided in the image. Arrange the following steps in the correct logical sequence to explain why the strong correlation between age and hip-hop enjoyment disappears in Plot (b) compared to Plot (a).
A researcher is developing a protocol to study how chronological age predicts various psychological preferences. To construct a data collection framework that avoids the specific statistical distortion shown in the provided scatterplots, where a strong population relationship () disappears in a narrow subgroup, which of the following sampling designs should be developed?
In the provided example, the Pearson's for the relationship between age and hip hop music enjoyment in the restricted age group ( to years) is reported as .
Based on the provided scatterplots illustrating the relationship between age and hip-hop enjoyment, match each sampling condition or statistical result with the statement that best explains its role in understanding range restriction.
A researcher collected data exclusively from - to -year-olds to study the relationship between age and hip hop enjoyment and found , concluding the two variables are unrelated. A critic argues this conclusion is invalid for the general population because the sample suffers from _____ of range, which obscures the true negative relationship () that emerges when participants across the full age spectrum are included.
In the age-and-hip-hop-music example, restricting data collection to participants aged 18 to 24 causes the Pearson's to drop from to because the narrow age band eliminates nearly all _____ in the age variable, making it impossible for the computed correlation to reflect the true population trend.
A psychology student reads a published study claiming that age does not predict hip hop music enjoyment () because the data were collected only from 18- to 24-year-olds. Order the following steps from first (1) to last (5) to properly evaluate whether the researcher's 'no relationship' conclusion is justified given the possibility of restriction of range.
Based on the provided example of range restriction, identify the Pearson's value representing the correlation between age and hip hop music enjoyment across the general population, the Pearson's value when the sample is restricted to - to -year-olds, and explain the general methodological recommendation derived from these findings.
Diagnose the statistical and design error in the researcher's study. Explain why her conclusion is misleading by referencing the correlation values expected across both the restricted group and the general population, and explain how she can correct her study's design.
If a research team is studying the relationship between age and hip hop music enjoyment but restricts their sample exclusively to people aged to , apply the principle of range restriction to predict what their calculated Pearson's will be and describe what they must do to obtain a correlation that reflects the true population trend of .