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# QAPHMP

### Doctoring Theory

Question | Answer |
---|---|

Epidemiology | the study of distribution and determinants of health-related states in specified populations and the application of this study to control health problems |

Distribution | Different criteria of people (age, sex, ethnicity, socioeconomic status, etc.) |

Determinants | risk factors and preventative factors (modifiable and non-modifiable) |

Incidence | Is a measure of disease frequency.a measure of the occurrence of new disease or change in state (the best outcome to study for epidemiology) – Deals a lot with exposure and risk of developing the disease |

How is cumulative incidence expressed? | as a percentage (# with disease / # at risk for the disease) |

How is Incidence rate expressed? | # of new cases/person-time |

Prevalence | a measure of disease frequency. It is the measurement of existing disease in a particular time period |

How is prevalence expressed? | (#with the disease) / total population. Sometimes shown as a percentage – don’t confuse with cumulative incidence! Usually used for chronic diseases (The number of people living with ______ disease) |

Rate ratio | the ratio between incidence rates of exposed vs. non-exposed. |

What is the null value for rates ratio or odds ratio? | Its null value is 1. A value < 1 suggests that those that are exposed are at a lower risk for disease than the non-exposed. A value > 1 suggests that those exposed are at a greater risk for disease than those not exposed. |

Epidemic | when there is a higher rate of disease than would be expected based on previous data. It is graphed as time vs. # of cases. Normally, the graph is flat, but during an epidemic, there is a large upward spike. |

What is the difference between experimental and observational studies? | in an experimental study, the investigator assigns the exposure to individuals. In an observational study, the exposure status is not determined by the investigator and thus can only be “observed.” |

What are the defining characteristics of a case-control study? | a case-control study is where individuals with the disease (cases) and individuals without the disease (controls) are picked and exposure is determined. |

What are the advantages of a case control study? | Efficiency, less-expensive, can study rare diseases, can study multiple exposures, can use existing records. |

What are the disadvantages of a case control study? | More potential for bias (disease has already occurred) in case selection and in how information on exposure is collected, more potential for confounding, records may be incomplete |

Identify the defining characteristic of a cohort study | Subjects are chosen/classified on the basis of exposure and are followed/traced to determine the outcome. |

(4)retrospective Cohort study advantages | can study rare exposures, can study multiple outcomes, can calculate incidence rate, may be less expensive if data is readily available |

(5)Retrospective Cohort study Disadvantages | Need a large sample, risk of loss of follow up data being present, poor information on exposure, more susceptible to bias, may be more expensive if data gathering needed |

(5)Prospective cohort study advantages | can study rare exposures, can study multiple outcomes, good information on exposure, can calculate incidence rates, bias less likely |

(3)Prospective cohort study disadvantages | requires a large sample, risk of loss of follow up, potential for uncontrolled confounding. |

Identify the defining characteristics of cross-sectional studies | subjects are enrolled in the study regardless or exposure/disease status. Exposure and disease are then measured simultaneously |

Identify the defining characteristics of ecological studies | correlation between exposure and health outcome at a population/geographic level. Used for hypothesis generation ONLY! No information on individuals – groups only. Susceptible to bias and confounding |

Identify the defining characteristics of an experimental study (clinical trial) | Subjects are assigned treatment/exposure by the investigator. Investigators then follow the subjects forward in calendar time until the disease/outcome occurs or the study ends. |

(3)Advantages of an experimental study/clinical trial | low bias and confounding because it is usually double blinded. You can study multiple outcomes for a single exposure better data quality. |

(3)Disadvantages of an experimental study/clinical trial | ethical risk more time and money than most may not be generalizable |

Identify the defining characteristic of a meta-analysis | systematic search of the lit for relevant studies meeting criteria for methodology & validity; results are combined and statistics applied for hypothesis testing & generating measure of outcome, p-values and/or confidence intervals |

(2)Advantages of meta-analysis | inexpensive, allows researcher to examine compare multiple studies and synthesize research in a meaningful way |

(3) Disadvantages of meta-analysis | Relies on existing data Bias Variability of the data |

Define a review | A review does not involve statistical techniques, it is just the author’s (skilled) opinion |

Define a Confidence interval | Used for significance testing. The numerical estimate of the measure of interest is ALWAYS within its confidence interval which is defined by a lower confidence limit and an upper confidence limit. |

Define a 95% Confidence interval | we have 95% confidence that the true value of the measure of interest lies within the CI. |

alpha error | a false positive, occurs when a statistical test rejects a true null hypothesis. e.g. if a null hypothesis states a patient is healthy, and the patient is indeed healthy, but the test rejects this hypothesis, falsely suggesting that the patient is sick. |

beta error | a false(-), occurs when the test fails to reject a false null hypothesis. e.g. if a null hypothesis states a patient is healthy, and the patient is in fact sick, but the test fails to reject the hypothesis, falsely suggesting that the patient is healthy. |

Power | is the probability that the null hypothesis will be rejected when it is in fact false; to increase study power, increase α |

What is a p value? | an attempt to answer the questions: what is the probability that I would get this result if the only explanation were chance? |

What does it mean if p < .05 (α) ? | the difference is real and not just due to chance reject the null hypothesis |

What does it mean if p > .05? | the difference is due to chance; DO NOT reject the null |

Mean | sum of measurements / # of observations; average |

Median | level below which 50% of the observations lie (or above which 50% of the observations lie) |

Mode | the most frequently occurring observation |

When is it most appropriate to use the mean? | for summarizing data that is close to a normal distribution (more affected by outlying data points). |

When is it most appropriate to use the median? | skewed data |

Describe and recognize the four measures of variability | Standard deviation Variance Percentiles (corresponds to median Range (corresponds to mode |

List the three characteristics of a normal or Gaussian distribution or curve | Symmetrical about its mean Mean = median = mode Bell-shaped |

List the (3) conditions necessary to justify, and the requirements for, a screening program | The disease is an important cause of mortality and/or morbidity. A proven and acceptable test exists to detect individuals at an early modifiable stage. There is safe and effective treatment available to treat the disease and its consequences |

Sensitivity | TP/(TP+FN) = among persons with disease, the percent that have a positive test |

Specificity | TN/(TN+FP) = among persons without disease, the percent that have a negative test |

Predictive Value Positive | TP/(TP+FP) = among persons with a positive test, the percent who have disease |

Predictive value negative | TN/(TN+FN) = among persons with a negative test, the percent who |

Bias | any trend in the collection, analysis, interpretation, publication or review of data that can lead to conclusions that are systematically different from the truth |

Selection bias | non-comparable criteria are used to select entrants into two groups of the study – most common when both exposure and disease have already occurred at the time the study begins |

Information bias (observation bias) | information is collected from the study groups in a non-comparable manner – ex |

cohort v. case control studies | cohort has 1 cohort & 2 exposures ( all have CVD, some take drug A, some don't) then evaluate; case control has 2 cohorts & 1 exposure (those with CVD, those without) all take Drug A then evaluate |

What is the relationship between prevalence and incidence? | P= I x duration |

Created by:
denpasar