Introduction to Biostatistics

• Biostatistics is the application of statistical methods to the life sciences like biology, medicine, and public health
• Descriptive Statistics:

  • Techniques for summarizing and presenting data in a form that will make them easier to analyze and interpret
• Inferential Statistics:

  • Concerned with making estimates, predictions, generalizations, and conclusions about a target population based on information from a sample
  • Includes estimation and hypothesis testing
• Classification of Statistical Data includes:

  • Demographic
  • Health Status
  • Health Resources
  • Health-related Socio-economic Environmental Factors
• Nominal : a classificatory scale where the categories are used as labels only; sex, race, blood group, patient ID
• Ordinal : used for categories which can be ordered or ranked; linkert scale, psychosocial scale
• Interval : same characteristics as ordinal; zero point is arbitrary and does not mean absence of the characteristic; temperature, IQ
• Ratio : same characteristics as ordinal; a meaningful zero point exist; weight, BP, height, doctor visits
• • Title - it should state the objective of the table. It should clearly, briefly and comprehensively describe what the figures in the body of the table stand for. How the data are classified, where and when obtained
  • Stubs - indicate the basis of classification of the rows or horizontal series of figures
• • Column headings - indicate the basis of classification of the columns or vertical series of figures.
  • Body of the table - this is made up of the figures filling the cells or compartments brought about by the coordinates of rows and columns
  • Marginal Totals - refer to the column totals and row totals
  • Footnote - indicate the source of information
• • Title - indicate clearly and briefly what the figures in the body of the graph stand for, how the data were classified, and where and when obtained. This is placed at the bottom of the graph, preceded by a number for easy reference.
  • Axis - a graph has 2 axes, the vertical and the horizontal
• • Legend - this is needed when one is drawing more than one graph in a graphing space. This clarifies what particular item each of the graph refers to. It is placed either at the bottom of the graph or as close as possible to the figures being identified.
  • Body of the graph - these are the lines, bars or figures drawn within the graphing
• • Frequency Distribution – there are two kinds of scales used, the qualitative and the quantitative which may discontinuous variety (counts) or continuous (measurement)
• • Trend – numbers (count) or raters (measurements) plotted over a given time period
• • Correlation data – maybe either of the two
• Probability 

  • Used to describe the variety and frequency of past outcomes under similar conditions as a way of predicting what should happen in the future 
• • P value – used to express the degree of probability or improbability of a certain result in an experiment. 
  • Expresses the probability that the observed result could have occurred by chance alone.
• Confidence Interval 

  • This is a range of values within which the true result probably falls. 
• The narrower the confidence interval, the lower the likelihood of random error.
• Confidential Interval

  • Are often expressed as margins of error, as in political polling, when a politician’s support might be estimated at 50 percent. The confidence interval would be 47% to 53% 
  • While p values and confidence intervals are useful concepts in deciding how seriously to take an experimental result, it is wrong to place too much confidence in an experiment just because it yields a low p value or a narrow confidence interval.
• Variable is the measurement of a characteristics
• Qualitative - variables whose categories are simply used as labels to distinguish one group from another

  • numerical representation of the categories are for labeling/coding and not for comparison 
  • sex, religion, place of residence, Disease status
• Quantitative – values indicate a quantity or amount and can be expressed numerically

  • values can be arranged according to magnitude 
  • age, height, weight, blood pressure
• Tabulation refers to the arrangement of any data in an orderly sequence, so that they can be presented concisely and compactly and so that they can be understood easily.
• Frequency distribution

  • Data are grouped according to some scale of classification, where the sum of the entries is equal to the total. The figures may either be in equal numbers, in percent, or in both. The scales used may be qualitative, quantitative, or both.
• • Frequency distributions are portrayed as frequency tables, histograms, or polygons.
• • Correlation data - used to compare two or more frequencies
  • Time series data - some variable changes over a while is the one being presented