Ratio, Rates, Vital Statistics

• Ratio 

  • also called a proportion of the quotient of the sum of the two numbers.
  • A good example is number of deaths per population
• Rate

  • ratio involving a time
  • count or measurement is observed over a period and then divided by its base or population of observation.
• Incidence Rate measures the frequency of occurrence of the phenomenon during a given period of time. Deals only with new cases.
• Prevalence rate measures the proportion of the population that exhibits a particular disease at a particular time. This can only be determined following a survey of the population concerned. Deals with total (OLD and NEW) number of cases.
• Incidence

  • Also known as attack rate, case, sickness rate morbidity rate
  • It refers to newly discovered cases of a particular disease
  • It answers the question “how frequent do cases of a particular disease occur during a given period of time”
  • Used when dealing with acute conditions and accidents
• Prevalence 

  • It refers to the newly discovered and old cases of a particular disease over a population
  • Used when dealing with chronic conditions and disabilities
  • It answers the question “what proportion of the group or population is actually ill with a particular disease at a point in time.
  • Usually determined by means of survey
• Crude Birth rate (CBR)

  • This is a measure of fertility of the population
  • the rate is called crude for the following reasons
  • Only live births are counted
  • The denominator is the total population which includes children, old people and males
  • The rate is expressed in population unit of 1000 to make the figures meaningful
• Crude Death Rate (CDR)

  • This is a measure of the risk of dying from all causes in a population.
• The Crude Birth Rate (CBR) and Crude Death Rate (CDR)

  • statistical values that can be utilized to measure the growth or decline of a population.
  • measured by the rate of births or deaths respectively among a population of 1000.
  • determined by taking the total number of births or deaths in a population and dividing both values by a number to obtain the rate per 1000.
• Maternal Mortality Rate (MMR) 

  • Measure the risk of dying due to the process of pregnancy, childbirth and puerperium.
  • It also measures the adequacy of maternal health services
• Infant Mortality Rate (IMR)

  • Measures the risk of dying due to infancy (under 1 year of age)
  • deaths under 1 year of age/ number of live births x 1000
• Neonatal Mortality Rate

  • Measures the risk of dying in the first four weeks of life of the infant (newborn)
  • The number of children dying under 28 days of age divided by the number of live births that year
  • (Number of infant death / number of life birth) X 1000
• Fetal Death Rate

  • Measures the risk of dying before birth
• Perinatal Mortality Rate

  • The word means around the period of birth (a month or more before births and one month after birth)
  • Measures the loss of life in later pregnancy and early infancy.