Biostatistics

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Author:
stevenfleek
ID:
175162
Filename:
Biostatistics
Updated:
2012-10-02 22:26:26
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Public Health Final SCUHS
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Public health
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  1. BIometry-Biostatistics
    What does it consist of?
    • Collection,    Classification
    • Description,  Analysis
    • Interpretation,  Presentation
  2. Stats (Types & Usage)
    • Descriptive & Analytical- summary measures of data
    • -Scientific method for interpreting data obtained

    • Vital Stats (PH agencies)- Birth, deaths, marriage, health related conditions
    • -Re-enforcement of other findings
    • -Statistical reasoning (clinical judgment, scientific judgment)
  3. DATA:
    Refer to individual values (3things)
    Properties (4 things)
    • Individual values: 1. presented 2.measured 3. observed
    • Properties: 1. sample population 2. grouped or ungrouped
    • 3. quantitative or qualitative 4. discrete or continuous
  4. Where do we get Data?
    Types of Sample population?
    • - from a population
    • -Types of sample populations :(simple random, non-random, Stratified selected)
  5. What is grouped? Ungrouped?
    • Groups= consist of identical data, by frequency
    • Ungroup= Presented individually(even if identical)
  6. Quantitative?
    Qualitative?
    Discrete?
    Continuous?
    • Quantitative( base on Number)
    • Qualitative (non-numerical, based on categories)
    • Discrete (distinct categories, limited # of possible values exist)
    • Continuous (Unlimited # of possible values)
  7. a. Accuracy?
    b. Precision?
    c. Reliability?
    d. Validity?
    • a. exactness, measure true value of what being studied
    • b. consisten and reproducible
    • c. stable, dependable, sound
    • d. measure what is supposed to measure
  8. a. Distribution
    b. Normal
    c. Skewed
    a. complete summary of frequenies or proportion of a characteristic for a series of data from a population or sample.

    b. AKA: Gaussian (continuous bell shape)

    c. (+) skewed= to the right, (-) skewed= to left
  9. Descriptive stats (Measure of central Affinity)

    1. Arithmetic Mean?
    2. Median?
    • 1. Mean (sensitive to extreme values in a series)
    •  - Add all #/ Total #'s in series

    • 2. Divides series into 2 equal groups  (not sensitive to extreme values), better representative of central tendency than mean.
    • - also it is the middle of Percentiles= Values divide series into defined percentages (level of measurment below which a specified portion of distribution falls)
    • - Middle number
  10. Continued:
    3. Median?
    4. Mode?
    5. Range?
    6. Variance?
    • 3. if ODD # of values (lowest--> highest and divide in 1/2)
    • - if EVEN # (2 values divide in 1/2, calcutae their mean)

    4. Most occuring values in a series (Epi studies for peak of disease occurance)

    5. Difference b/w highest and lowest value (measure data spread)

    • 6. Main use to calculate standard deviation
    • -SD= +ve sq. root of the variance
  11. Analytical stats.
    7. Probability?
    8. Rule of probability?
    9. Null hypothesis
    • 7. quant. expression of likelihood of occurrence
    • - defined in terms of relative frequency (never >1 or <0)

    • 8. PR (A does not occur)= 1- PR (A occurs)
    • -PR (A/B)= # of times A&B occur jointly or of times B occurs

    • 9. Samples compared are similar (any difference is due to chance)
    • - used to define significant difference
  12. Screening
    1.theories
    2.programs
    3.sensitivity
    4.specificity
    • - testing or examining individual or large groups of people
    • -It separates from those who have high probability of having condition under study.

    1. Theories concerned w/ diseases, diagnostic testing, used as a case finding tool, and treatment testing.

    • 2. Programs (must meet certian criteria)
    • -Segment being screened @ relatively high risk for cond.
    • -the disease= of enough concern to community being screened
    • -Un-diagnosed disease= should be more responsive to TX than if diagnosed @ later symptomatic stage

    • (screening test are: sensitive/specific, applicable to Lg #, easy and quick, should not cause harm, inexpensive)
    • (Those with (+) results guaranteed follow up evaluation)
  13. 3. Senitivity?
    4. Specificty?
    • 3. ability to ID correctly those who do NOT HAVE the disease (if 100% sensitivity= (-))
    • -ability of the test to give a (+) result when person tested truly has disease.
    • - Is a %

    • 4. ability to ID correctly those who have the disease (if 100%= (+))
    • -ability to test to give a (-) result when person tested is free of disease
    • -Is a %
  14. Setting Cut-off? depends on?
    • -Natural Hx of disease
    • -effectiveness of intervention (early or late)
    •     -if disease is rare: Sensitivity=high (or cases present will be missed)
    •     -If very lethal (early detection improves prognosis)
    • (high sensitivity is necessary)(false + are tolerated, false -'s are not)

    Screening if very rewarding (high sensitivity)

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