During the 1936 United States presidential election, pollster George Gallup successfully predicted that Franklin Roosevelt would win in a landslide by utilizing scientific methods with much smaller samples. By publicly criticizing the Literary Digest's methods prior to the election and correctly guaranteeing his own prediction, Gallup demonstrated the effectiveness of careful survey methodology.

George Gallup's 1936 Election Prediction

Match each element of the 1936 Literary Digest straw poll with its correct description.

The 1936 Literary Digest straw poll was a survey conducted to predict the outcome of the presidential election between Alf Landon and Franklin Roosevelt. The magazine attempted to forecast the results by sending ballots, which were also subscription requests, to millions of Americans. Based on this method, the editors incorrectly predicted that Landon would win in a landslide.

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Sampling bias is a systematic error that occurs when the method used to select participants results in a sample that fails to accurately represent the broader target population. Because the selected individuals differ in important ways from the overall group, any statistical findings derived from this unrepresentative sample will likely be inaccurate and cannot be safely generalized.

Sampling Bias

A sampling frame is essentially a comprehensive list of all members of a specified population from which a researcher will select respondents. Sources for these frames can include telephone directories, lists of registered voters, hospital records, or even geographic maps. Establishing an accurate sampling frame is a necessary prerequisite for conducting most forms of probability sampling.

Sampling Frame

The methodological roots of survey research can be traced back to English and American social surveys from the turn of the $$20$$th century, which aimed to systematically document widespread social issues such as poverty. In the $$1930$$s, the methodology progressed significantly as the United States government initiated nationwide surveys to assess social and economic conditions. The necessity to draw accurate inferences about the entire population from these surveys spurred crucial advancements in sampling techniques.

Origins of Survey Research

A straw poll is a type of survey. For example, during the 1936 presidential election, the Literary Digest conducted a straw poll by distributing ballots, which also functioned as subscription requests, to millions of Americans in an attempt to predict the election's outcome.

Straw Poll

https://kpu.pressbooks.pub/psychmethods4e/

KPU Research Methods in Psychology - 4th American Edition


**Context**: Let's say we have a neurologist from Hospital X who wants to investigate the relationship between cancer and stroke risk in the general population with a case-control study. The cases are all the neurologist's patients with a history of strokes. The control group consists of all her patients without a stroke history. Both groups were assessed for cancer. 

**How it Relates to Selection Bias**: Patients in the hospital may be more predisposed to those conditions or may have been brought to the hospital for those conditions. Therefore, they may be overrepresented in the study compared to the general population.

Example: Selection Bias in Case-Control Studies

Take Tobacco case as an example, the number of cancer patients admitted to hospital is by no means representative of the entire population, or even of smokers.

Another example of selection bias in Case-control Studies


- The COVID-19 testings tend to focus on already hospitalized people, not accounting for the people with mild symptoms and the asymptomatics leading to selection bias.  
- The differences in death rates across countries may not be attributed to clinical, demographic, and environmental factors.  
- Together with random sampling/testing, the Bayesian Network model allows causal explanations from data for better predictions.  


Summary of "COVID-19 infection and death rates: the need to incorporate causal explanations for the data and avoid bias in testing"

Non-response bias is a specific form of sampling bias that occurs when individuals who choose not to participate in a survey differ systematically from those who do complete it. Even when a study employs careful random sampling, this bias can skew results and lead to inaccurate conclusions because the final respondents no longer accurately represent the original intended sample.

Non-response Bias

1936 Literary Digest Straw Poll

What type of systematic error occurs when the method used to select participants results in a sample that fails to accurately represent the broader target population?

Stratified random sampling is a probability sampling method where a target population is first divided into distinct subgroups, known as strata, often based on demographic traits. After these groups are established, a simple random sample is drawn independently from each stratum, ensuring that various segments of the population are represented appropriately in the study.

Stratified Random Sampling

Simple random sampling is a method for obtaining a study sample where every single member of the target population has an equal chance of being selected. While this approach is effective for ensuring a representative sample, it is often difficult or impossible to achieve in psychological research because populations are rarely defined clearly enough to give everyone an equal selection chance.

Simple Random Sampling

Which of the following provides the best definition of a sampling frame?

Following its success in election polling and market research, survey methodology expanded into academic fields like sociology and public health before becoming prominent in psychology during the $$1930$$s. Psychologists advanced questionnaire design by developing tools like the Likert scale and applied survey methods to study social psychological phenomena such as attitudes, prejudice, and stereotypes. Furthermore, early attitude researchers pioneered the use of larger and more diverse samples, moving beyond the convenience samples of university students that were typically used in the field.

Early Applications of Survey Research in Psychology

What crucial methodological advancement was directly spurred by the need to draw accurate inferences about the entire population from nationwide government surveys in the 1930s?

During the 1936 presidential election, the Literary Digest distributed ballots to millions of Americans in an attempt to predict the election's outcome. This is a historical example of which type of survey?

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