Biostatistics

• Collection,    Classification
• Description,  Analysis
• Interpretation,  Presentation

• 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)

• Individual values: 1. presented 2.measured 3. observed
• Properties: 1. sample population 2. grouped or ungrouped
• 3. quantitative or qualitative 4. discrete or continuous

• - from a population
• -Types of sample populations :(simple random, non-random, Stratified selected)

• Groups= consist of identical data, by frequency
• Ungroup= Presented individually(even if identical)

• Quantitative( base on Number)
• Qualitative (non-numerical, based on categories)
• Discrete (distinct categories, limited # of possible values exist)
• Continuous (Unlimited # of possible values)

• a. exactness, measure true value of what being studied
• b. consisten and reproducible
• c. stable, dependable, sound
• d. measure what is supposed to measure

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

• 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

• 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

• 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

• - 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)

• 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 %

• -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)