Unit 3 – Public Health Statistics Chapter 7 – Statistics: Making Sense of Uncertainty

Statistics is: The numbers that describe the health of the population The science used to interpret these numbers

The Uncertainty of Science Most science is of a probable nature Science is ongoing – studies may contradict each other The science of statistics can quantify the degree of uncertainty

Probability The probable is what usually happens P value: p=0.05 is usually taken to mean a result is statistically significant However, when p=0.05, there is still a 5% chance that the result is wrong Confidence interval; Law of small probabilities

Power of a Study The probability of finding an effect if there is, in fact, an effect Large numbers confer power

Statistics of Screening Tests Examples of screening: Mammography for breast cancer HIV tests Newborn screening Sensitivity vs. specificity False positives vs. false negatives

Rates Relate the raw numbers to size of population Birth rates Mortality rates Crude rates Adjusted rates E.g., age adjusted Group specfic rates E.g., gender specific

Other Calculated Statistics Life expectancy Years of potential life lost (YPLL)

Risk Assessment and Risk Perception For well-known risks, can be calculated from historical data For poorly understood risks, must make many assumptions Risk perception involves psychological factors

Cost-Benefit Analysis Cost is easier to calculate than benefit What monetary value to put on a life saved Often controversial Cost-effectiveness analysis

Unit 3 – Public Health Statistics Chapter 8 – The Role of Data in Public Health

Uses of Data Assess the health of a community Raw material for research

Collection of Data Local records Birth certificates Death certificates Notifiable diseases Other vital statistics Transmitted from local governments to states Transmitted from states to National Center for Health Statistics (part of CDC) Surveys

The Census Serves as denominator for most public health data Age, sex, race, ethnicity Every 10 years American Community Survey done in between, on an ongoing basis Education, housing, health insurance

Surveys National Health Interview Survey (NCHS) National Health and Nutrition Examination Survey (NCHS) Behavioral Risk Factor Survey (BRFSS) – state-by- state, with results transmitted to NCHS Youth Behavioral Risk Factor Survey – state-by- state with results transmitted to NCHS Other surveys done by other government agencies

Accuracy and Availability of Data Data collection is imperfect Census is most accurate; still there are overcounts and undercounts Information technology increases accuracy and availability

Confidentiality of Data Governments have safeguards to protect individual Use of data may involve removal of identifying information on individuals Use of data requires institutional review boards or data protection committees