Statistics: Hosmer-Lemeshow Goodness of Fit Test and ROC Curve
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Questions and Answers

What is the primary purpose of a ROC curve?

  • To estimate the time until an event occurs
  • To evaluate the goodness of fit of a model
  • To distinguish between high-risk and low-risk patients (correct)
  • To compare the survival rates of two groups

    • What is the typical range of AUC values for a 'good' model?

  • 0.92 to 0.97
  • 0.50 to 0.75
  • 0.75 to 0.92 (correct)
  • 0.97 to 1.00

    • When would you use survival analysis instead of logistic regression?

  • When the time to an event is important (correct)
  • When there are multiple predictors
  • When the data is normally distributed
  • When the outcome is binary

    • What is the Kaplan-Meier estimation used for?

    <p>To estimate the survival function</p> Signup and view all the answers

    What is the purpose of the Log Rank Test?

    <p>To compare the survival rates of two groups</p> Signup and view all the answers

    What is the Cox Proportional Hazard Model used for?

    <p>To analyze the relationship between predictors and survival time</p> Signup and view all the answers

    What does a high AUC value indicate?

    <p>The model is excellent</p> Signup and view all the answers

    What is the Hosmer-Lemeshow test used for?

    <p>To evaluate the goodness of fit of a model</p> Signup and view all the answers

    What is the primary focus of the medical perspective in disease management?

    <p>Prognostic</p> Signup and view all the answers

    What is the risk of dying within 30 days post MI for a 75-year-old patient compared to a 50-year-old patient?

    <p>Lower for the 50-year-old patient</p> Signup and view all the answers

    What is the primary function of diagnosis in disease management?

    <p>To determine signs and symptoms</p> Signup and view all the answers

    What is the primary concern of the therapeutic perspective?

    <p>Treating the disease</p> Signup and view all the answers

    What is the primary focus of the etiology perspective?

    <p>Determining the cause of the disease</p> Signup and view all the answers

    What is the significance of the 30-day mortality rate post-MI?

    <p>It is a measure of the risk of dying within 30 days</p> Signup and view all the answers

    What is the purpose of identifying risk factors in disease management?

    <p>To identify individuals at high risk of developing the disease</p> Signup and view all the answers

    What is the significance of the population at risk in disease management?

    <p>It refers to the group of people who are at high risk of developing the disease</p> Signup and view all the answers

    What is the 10-year risk of CHD event for a 45-year-old male with a total score of 7?

    <p>13%</p> Signup and view all the answers

    What is the benefit of controlling BP and improving diet in the given scenario?

    <p>Reduce risk from 13% to 4%</p> Signup and view all the answers

    What type of study design is typically used in prognostic research?

    <p>Cohort study</p> Signup and view all the answers

    What is the goal of Phase I in a two-phase prognostic study?

    <p>To come up with the prediction rule</p> Signup and view all the answers

    What is the relationship between the determinants and the outcome in a prognostic study?

    <p>Endpoint is a function of the combination of determinants</p> Signup and view all the answers

    What is the first step in conducting a prognostic study?

    <p>Identify the research question</p> Signup and view all the answers

    What is the purpose of Phase II in a two-phase prognostic study?

    <p>To test the predictive ability of the model</p> Signup and view all the answers

    What is the characteristic of a prognostic study?

    <p>It is longitudinal in nature and involves multiple risk factors</p> Signup and view all the answers

    What is the primary goal of a prognostic study?

    <p>To estimate the probability of a future outcome given all determinants</p> Signup and view all the answers

    What type of risk does a prognostic study measure?

    <p>Absolute risk</p> Signup and view all the answers

    What is the purpose of informing a patient about their prognosis?

    <p>To help decide whether to start an intervention or treatment</p> Signup and view all the answers

    What is the characteristic of an individual patient that is considered non-clinical?

    <p>Age</p> Signup and view all the answers

    What is the benefit of knowing an individual patient's risk of developing a specific outcome?

    <p>It helps in deciding whether to start an intervention or treatment</p> Signup and view all the answers

    What is the purpose of a prognostic study in terms of treatment or intervention?

    <p>To predict how much changes in risk after the treatment or intervention</p> Signup and view all the answers

    What is the term used to describe the risk of an individual patient having a specific outcome?

    <p>Individual prognosis</p> Signup and view all the answers

    Why is it important to know an individual patient's characteristics?

    <p>To estimate the probability of a future outcome</p> Signup and view all the answers

    What is the purpose of defining a relevant outcome in a prognostic study?

    <p>To measure the effect of the determinant status</p> Signup and view all the answers

    Why is it essential to measure the outcome in all patients in a prognostic study?

    <p>To ensure the outcome is measured as precisely as possible</p> Signup and view all the answers

    What is the purpose of checking for non-linearity of continuous variables in model development?

    <p>To determine the best model for the data</p> Signup and view all the answers

    What is the formula for logistic regression analysis?

    <p>Y ~ α + βX</p> Signup and view all the answers

    What is the purpose of regression coefficients in logistic regression analysis?

    <p>To calculate the risk of disease presence</p> Signup and view all the answers

    What is the purpose of blinding in a prognostic study?

    <p>To eliminate bias in the study</p> Signup and view all the answers

    What is the purpose of defining a relevant time period for prognosis?

    <p>To measure the effect of the determinant status</p> Signup and view all the answers

    What is the formula to calculate the odds ratio in logistic regression analysis?

    <p>Exp(B) = odds ratio</p> Signup and view all the answers

    Study Notes

    Prognostic Study

    • Aims to predict the probability of an individual patient experiencing a particular outcome or event
    • Focuses on the risk of an individual patient, rather than the average population risk or relative risk compared to others

    Types of Prognostic Study

    • Longitudinal in nature, involving multiple risk factors/predictors
    • Absolute risk prediction
    • Study design: Cohort study
    • Cohort is a group that is followed in time, where exposure is present before the outcome

    Phases of Prognostic Study

    • Phase 1: Develop a prediction rule
    • Phase 2: Test the predictive ability of the prediction rule (validation of model in new population)

    Steps in Prognostic Research

    • Identify research question
    • Define study population (domain/population)
    • Identify prognostic factors (determinants-indicator/intervention/control)
    • Follow clinical practice

    Measuring Outcomes

    • Define a relevant outcome (e.g. death, disability, quality of life, MI)
    • Define a relevant time period for prognosis (e.g. days, weeks, years)
    • Measure outcome in all patients as precisely as possible

    Analysis in Prognostic Study

    • Model development: univariate analysis, check non-linearity of continuous variables, multivariate analysis, check for interaction
    • Easy to use format of model
    • Performance of model

    Logistic Regression Analysis

    • Y ~ α + βX
    • Y ~ intercept + coef* factor
    • Regression coefficients (beta, β) used to calculate risk of disease presence
    • Exp(β) = odds ratio

    Hosmer-Lemeshow Goodness of Fit Test

    • Used to assess the goodness of fit of a logistic regression model
    • Measures the difference between observed and predicted outcomes

    Discrimination

    • Ability of a model to distinguish between high-risk and low-risk patients
    • ROC curve (Receiver Operating Characteristic) and AUC (Area Under the Curve) used to evaluate discrimination
    • AUC values:
      • 0.50 to 0.75: fair
      • 0.75 to 0.92: good
      • 0.92 to 0.97: very good
      • 0.97 to 1.00: excellent

    Survival Analysis

    • Used to analyze the time to an event (e.g. time to death, time to disease occurrence)
    • Kaplan-Meier estimation and Log Rank Test used to estimate survival function and compare survival curves between groups
    • Cox Proportional Hazard Model used to analyze the effect of multiple predictors on survival time

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    Description

    This quiz assesses understanding of statistical concepts, including the Hosmer-Lemeshow goodness of fit test and the ROC curve, used to measure model performance and discrimination in predicting outcomes.

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