PSYC 2019H - Lecture 3: Sampling and Probability
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Questions and Answers

What is the definition of expected relative-frequency probability?

  • The probability of an event occurring based on a specific set of conditions.
  • The long-term probability of an event occurring based on many trials. (correct)
  • The likelihood of an event occurring, based on the actual outcome of a single trial.
  • The theoretical probability of an event occurring, based on mathematical calculations.

    • In the M&M example, what is the purpose of putting the M&M back in the bag after each trial?

  • To make sure the percentage of red M&Ms remains constant.
  • To minimize the impact of individual trials on the overall results.
  • To ensure a fair and unbiased sample. (correct)
  • To make the experiment easier and faster.

    • What is the relationship between probability, proportion, and percentage?

  • Percentage is simply probability multiplied by 100, but the proportion is distinct from both.
  • Both probability and proportion represent the number of successes divided by the number of trials. (correct)
  • Proportion is the number of trials divided by the number of successful outcomes.
  • Probability is the theoretical value, while proportion and percentage are used to represent actual outcomes.

    • What is the requirement for individual trials in statistical probability?

    <p>They must be unbiased and independent from each other. (C)</p> Signup and view all the answers

    What is the purpose of inferential statistics?

    <p>All of the above. (D)</p> Signup and view all the answers

    What is a null hypothesis?

    <p>A statement suggesting that there is no difference between populations. (C)</p> Signup and view all the answers

    What typically happens when the null hypothesis is rejected?

    <p>The results indicate that there is a significant difference between groups. (B)</p> Signup and view all the answers

    What is the main difference between a control group and an experimental group?

    <p>The control group serves as a baseline comparison, while the experimental group receives the treatment. (A)</p> Signup and view all the answers

    What does failing to reject the null hypothesis imply about the research hypothesis?

    <p>There is insufficient evidence to support the research hypothesis. (D)</p> Signup and view all the answers

    What occurs during a Type I error in hypothesis testing?

    <p>Rejecting the null hypothesis when it is true. (B)</p> Signup and view all the answers

    In what situation would a Type II error occur?

    <p>Failing to reject the null hypothesis when it is false. (A)</p> Signup and view all the answers

    Which statement accurately reflects the consequences of a Type I error?

    <p>It suggests that a difference exists when it does not. (A)</p> Signup and view all the answers

    Which of the following is likely to cause reporting bias in research results?

    <p>Prioritizing positive outcomes over null results. (D)</p> Signup and view all the answers

    What is a potential drawback of convenience sampling?

    <p>It may not accurately reflect the larger population. (A)</p> Signup and view all the answers

    Which hypothesis is indicated when researchers fail to find a statistically significant difference?

    <p>The null hypothesis is likely true. (D)</p> Signup and view all the answers

    In hypothesis testing, what does the null hypothesis typically represent?

    <p>No change or difference. (B)</p> Signup and view all the answers

    What does a sample represent in research?

    <p>A set of observations from the population of interest (C)</p> Signup and view all the answers

    Which type of sampling ensures every member of the population has an equal chance of selection?

    <p>Random sample (B)</p> Signup and view all the answers

    What is a major disadvantage of convenience sampling?

    <p>Lower external validity (A)</p> Signup and view all the answers

    What do 'COG' statements refer to in research?

    <p>Constraints on generality statements (A)</p> Signup and view all the answers

    Which concept refers to the tendency to favor information that confirms existing beliefs?

    <p>Confirmation bias (B)</p> Signup and view all the answers

    What is 'personal probability' in the context of psychology?

    <p>A person's judgment about event likelihood (D)</p> Signup and view all the answers

    What does the term 'replication' refer to in scientific research?

    <p>The repetition of scientific results in a different context (A)</p> Signup and view all the answers

    What does probability measure in research?

    <p>The likelihood of a particular outcome occurring (D)</p> Signup and view all the answers

    Flashcards

    Relative-Frequency Probability

    The likelihood of an event based on many trials' outcomes.

    Calculating Probability

    Divide the number of successful outcomes by total trials.

    Probability vs Proportion

    Probability is the expected long-run proportion of outcomes.

    Percentage

    Probability or proportion multiplied by 100.

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    Null Hypothesis

    Postulates no difference between populations.

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    Alternative Hypothesis

    Postulates a difference in a certain direction between populations.

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    Control Group

    Does not receive the treatment in an experiment.

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    Experimental Group

    Receives the treatment to test effects.

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    Population

    The entire group of observations we want to study.

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    Sample

    A subset of observations drawn from the population.

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    Random sample

    Every member of the population has an equal chance of being selected.

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    Convenience sample

    A sample using participants who are readily available.

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    Generalizability

    The extent to which findings can be applied to other contexts.

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    Replication

    Duplicating scientific results in different contexts or samples.

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    Confirmation Bias

    Tendency to focus on evidence that confirms existing beliefs.

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    Personal Probability

    An individual's judgment about the likelihood of an event occurring.

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    Research Hypothesis

    A statement that indicates there will be a change or difference.

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    Type I Error

    Rejecting the null hypothesis when it is actually true.

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    Type II Error

    Failing to reject the null hypothesis when it is false.

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    Fail to Reject Null Hypothesis

    No statistical evidence to support the research hypothesis.

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    Reject Null Hypothesis

    Statistical evidence that supports the research hypothesis.

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    Statistical Significance

    The likelihood that a result is not due to chance.

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    Sampling Method

    The technique used to choose participants for a study.

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    Study Notes

    PSYC 2019H - Lecture 3: Sampling and Probability

    • Topics covered include samples and populations, probability, inferential statistics, and type I and II errors.

    Samples and Populations

    • Population: Includes all possible observations researchers want to know something about.
    • Sample: A set of observations taken from the population of interest.

    Samples and Populations - Types of Samples

    • Random sample: Every member of the population has an equal chance of being selected for the study.
    • Convenience sample: Uses participants readily available. A major disadvantage is a potentially limited ability to apply findings to other samples or contexts (external validity).
    • WEIRD samples: Western, Educated, Industrialized, Rich, and Democratic. This is a common, but often criticized, sampling type that may not reflect broader populations.

    Samples and Populations - Addressing Generalizability Concerns

    • Replication: The duplication of scientific results in different contexts or with samples having different characteristics. This helps verify findings aren't specific to a single sample/context.
    • Constraints on generality (COG) statements: Statements outlining the target population to which study results should generalize.

    Probability

    • Psychology and other sciences use probabilistic reasoning.

    Probability - Enemies of Reason

    • Anecdotal evidence: Personal stories or isolated examples. This can be misleading as it ignores broader trends.
    • Confirmation bias: Unintentional tendency to prioritize confirming existing beliefs while ignoring contradicting evidence.
    • Illusory correlation: Believing an association exists between variables when there isn't any.

    Probability - Types of Probabilities

    • Personal probability: A person's own judgment about the likelihood of an event occurring.
    • Probability: The likelihood that a particular outcome will occur out of all possible outcomes.
    • Expected Relative-Frequency Probability: The likelihood of an event based on the outcome of many repeated trials.

    Probability Calculation Example

    • An example uses a bag of M&Ms to demonstrate calculating the probability of picking a red one at random. This involves repeating steps of picking an M&M and recording its colour multiple times, calculating the percentage of red M&Ms.

    Calculating Probability

    • Step 1: Determine the total number of trials.
    • Step 2: Calculate the number of successful trials (e.g., selecting red M&Ms).
    • Step 3: Divide the number of successful outcomes by the total number of trials to determine probability.

    Probability, Proportion, and Percentage

    • These terms are often confused.
    • Probability: Proportion expected over the long run.
    • Proportion or Relative frequency: Number of successes divided by the total number of trials.
    • Percentage: Probability multiplied by 100.
    • Statistical probability assumes consistent, independent trials.

    Inferential Statistics

    • Inferential statistics makes inferences about a population from sample data. This means making reasoned assumptions about the population, based on examining a smaller selection (sample) from that population.
    • It helps researchers determine if observed differences in samples are due to chance or if there's a real effect.

    Inferential Statistics - Hypotheses

    • Null hypothesis: States there's no difference between populations or that differences are in the opposite direction than hypothesized.
    • Research hypothesis (alternative hypothesis): States there's a difference in a particular direction.

    Inferential Statistics - Groups Related to Hypotheses

    • Control group: Does not receive the treatment.

    • Experimental group: Receives the treatment.

    Making a Decision About Hypotheses

    • Reject the null hypothesis: If data suggests a mean difference. Conclusion: there likely is a real effect.
    • Fail to reject the null hypothesis: If data doesn't support a mean difference. Conclusion: there's no strong evidence of a real effect.

    Inferential Statistics - Hypothesis Testing

    • Null hypothesis: No change or difference.
    • Research hypothesis: Change or difference.
    • Outcomes from hypothesis testing involve either rejecting or failing to reject the null hypothesis. These decisions depend on the research hypothesis being either supported or not.

    Type I and Type II Errors

    • Type I error: Rejecting a true null hypothesis (false positive).
    • Type II error: Failing to reject a false null hypothesis (false negative).

    Data Ethics: Prevalence of Type I Errors

    • Positive findings are frequently reported more than negative findings. This suggests a bias in the reporting of research studies.

    Study Notes - General

    • These notes cover the sampling method in research (random or convenience method), what the population might look like to the researcher and how well the samples might represent the populations, important issues of generalizing the results of research to other settings.

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    Related Documents

    PSYC 2019H Lecture 3, Winter 2022 PDF

    Description

    This quiz covers key concepts from PSYC 2019H Lecture 3, focusing on sampling types and probability. It discusses the differences between populations and samples, including random, convenience, and WEIRD samples. Additionally, it addresses generalizability and issues related to inferential statistics.

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