Statistics

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Statistics

  1. 1. What is Data?Data are facts or figures from which conclusion may be drawn. OrData is a collection of facts, such as values or measurements.It can be numbers, words, measurements, observations or even justdescriptions of things.Data are the raw material of statistics. Statistical analysis cannot proceed until the datainterest in an investigation are assembled and organized in a useful manner. We shallrefer to the data collected for a particular study as a Data Set.Each Data set contains observations on the variables of interest for the elements in thedata set.Elements: A data set represents a collection of elements (Country), and for eachelement information on one or more characteristic of interest (Birth Rate) is included inthe data set e.g.,Country Birth RateA 19.8B 20.7C 25.8 Prepared By: Sayed Burhan Atal
  2. 2. Conti.Qualitative vs QuantitativeData can be qualitative or quantitative.Qualitative data is descriptive information (it describes something)Quantitative data, is numerical information (numbers).And Quantitative data can also be Discrete or Continuous:Discrete data can only take certain values (like whole numbers)Continuous data can take any value (within a range)Put simply: Discrete data is counted, Continuous data is measured
  3. 3. Types of Data Data Quantitative Qualitative (Numeric) (Non - Numeric)
  4. 4. Variable A quantity that, varies from an individual to individual. Or A characteristic that can take on different possible outcomes is called a Variable. Variable Qualitative (Non - Numeric): If theQuantitative (Numeric) : If the outcome outcomes refer to non-numerical qualitiesAre expressed numerically, the variable or attributes, the variable is said to be is said to be quantitative. qualitative.
  5. 5. Population etc.Population: The totality of elements (persons, farms, firms) under study is called the population.Census: A survey that includes every element in the population is called a census.Sample and Sample Survey: A sample is a portion of the population. A survey that includes only a portion of the population is called a sample survey.
  6. 6. OBSERVATIONS AND VARIABLESObservations: In statistics, an observation often means any sort ofnumerical recording of information, whether it is a physicalmeasurement such as height or weight; a classification such asheads or tails, or an answer to a question such as yes or no.Variable: A characteristic that varies with an individual or anobject, is called a variable.For example, age is a variable as it varies from person toperson. A variable can assume a number of values.
  7. 7. Statistics deals with numbers Need to know nature of numbers collected 1. Continuous variables: type of numbers associated with measuring or weighing; any value in a continuous interval of measurement.  Examples: – Weight of students, height of plants, time to flowering 1. Discrete variables: type of numbers that are counted or categorical  Examples: – Numbers of boys, girls, insects, plants
  8. 8. Can you figure out… Which type of numbers (discrete or continuous?) – Numbers of persons preferring Brand X in 5 different towns – The weights of high school seniors – The lengths of oak leaves – The number of seeds germinating – 35 tall and 12 dwarf pea plants – Answers: all are discrete except the 2nd and 3rd examples are continuous.
  9. 9. EXAMPLES OF DATAData are collected in many aspects of everyday life.• Statements given to a police officer or physician or psychologist during an interview are data.• The correct and incorrect answers given by a student on a finalexamination.• Almost any athletic event produces data.• The time required by a runner to complete a marathon,• The number of errors committed by a baseball team in nine inningsof play, and• So on.
  10. 10. QUANTITATIVE & QUALITATIVE VARIABLES Variables may be classified into quantitative and qualitative accordingto the form of the characteristic of interest.• A variable is called a quantitative variable when a characteristic can beexpressed numerically such as age, weight, income or number of children. On the other hand, if the characteristic is non-numerical such aseducation, sex, eye-colour, quality, intelligence, poverty, satisfaction, etc.• where the variable is referred to as a qualitative variable. A qualitativecharacteristic is also called an attribute. An individual or an object with such a characteristic can be counted orenumerated after having been assigned to one of the several mutually exclusiveclasses or categories.

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