Lecture 1 Statistics PDF

STATISTICS It is a science concerned with scientific methods of collecting, summarizing, presenting and analyzing data. This analyzing may lead to conclusions and subsequent decisions. Medical statistics The science of medical statistics uses those statistical pertaining to the me...

STATISTICS It is a science concerned with scientific methods of collecting, summarizing, presenting and analyzing data. This analyzing may lead to conclusions and subsequent decisions. Medical statistics The science of medical statistics uses those statistical pertaining to the medical field, often unit of interest is a living person rather than some abstract phenomenon, object. i.e. statistics is a scientific approach to information presenting it self in numerical form which enable us to maximize our understanding of such information. Sometime the figures which result from statistical analysis are also referred to as statistics. Statistics can be broadly divided into two parts :- I. Descriptive statistics, dealing with methods for organizing a large mass of data, may be by : tabular, diagrammatic or numerical. i.e. they present a summary of the data which in their raw form are not easy to comprehend. II. Analytical statistics, (Inferential statistics), dealing with methods that enable a conclusion to be drawn from the data. Populations & Samples A large mass or group of data is called a population which can be finite or infinite. A small part of this group which tells the investigator about the population is called a sample. Because of chance, different samples give different results and this must be taken into account when using a sample to make inferences about the population, this phenomenon is called sampling variation. The number of individuals is called sample size. Data analysis and presentation of results The raw data are any mass collected data which have not been organized numerically and since this data are not very easy to understand ,it often helps to illustrate them with a diagram which should always be clearly lapelled and self explanatory ,so list the categories (classes) given, then count the number of observations in each category. These counts are called frequencies ,while the frequencies presented as percentages of the total number of individuals are called relative frequencies. General rules for forming a frequency distribution When the raw data is discrete or continuous we can form a frequency distribution table by using the followings: 1. Determine the range of values which is the difference between the largest and smallest values i.e. R = XMAX − XMIN +1 2. Find a convenient number of classes (NC) usually list between 5