1. Different types of variables

2. Issues to cover – in a flash 1.Quantitative variable (numeric variables) –1.1 Discrete variable –1.2 Continuous variable 2. Qualitative variable (Categorical variable) –2.1 Nominal variable –2.2 Binary variable –2.3 Ordinal variable

3. TYPES OF VARIABLES QUALITATIVE VERSUS QUANTITATIVE CONTINUOUS VERSUS DISCRETE NOMINAL, ORDINAL, INTERVAL, RATIO DEPENDENT VERSUS INDEPENDENT EXPOSURE VERSUS OUTCOME HIGHLY CONFUSING!!!

4. VARIABLES QUALITATIVEQUANTITATIVE CONTINUOUSDISCRETE

5. 1. Quantitative variable 1.1 Discrete variable: A variable which can only take certain values, usually whole numbers (a count) –Examples number of visits to a doctor, number of asthma episodes in a year, number of children in a household etc. 1.2 Continuous variable: a variable which can theoretically take any value within a given range –Examples: height, body mass index etc.

6. 2. Qualitative variable (Categorical variable) A variable whose values are represented by names or labels of the same characteristic. Examples are ethnicity, blood group, eye colour, nationality. All qualitative variables are discrete

7. 2.1 Nominal variable (Categorical variable) Categorical variables where the categories are not ordered in increasing or decreasing quality or intensity. E.g. Hair colour Other examples?

8. 2.2 Binary variable A categorical variable which takes only two categories or possible values. –Examples: Yes/No, Dead/Alive, Positive/Negative Other examples?

9. 2.3. Ordinal variable A categorical variable in which the different levels of the variable are ordered. Successive levels represent “increases” or “decreases” in the characteristic conveyed by the variable. Examples: –Severity of pain: no pain, minimal pain, moderate pain, severe pain –Grades of malnutrition categorized by BMI (Mild, moderate and severe)

10. Ordinal variables It is important to analyse this type of data with special methods E.g. chi square for trend, Kruskal-Wallis test (non-parametric significance test) and not with methods used for nominal variables

11. Discrete variable consists of separate, indivisible categories. –E.g., no. of children in a family, no. of students attending class. For a continuous variable, there are an infinite number of possible values that fall between any two observed values. –E.g., time, height, weight.

12. Nominal scale consists of set of categories that have different names; no order e.g., sex, religion, red-blue-green, Ordinal scale consists of set of categories that are organized in an ordered sequence. e.g., ranking the employees, stages of breast cancer, mild-moderate-severe Interval scale consists of ordered categories where all of the categories are intervals of exactly the same size. e.g., Temperature(in Celsius or Fahreinheit) Ratio scale is an interval scale with additional feature of an absolute zero point. e.g., Temperature(in Kelvin), height, weight

13. CAUSEEFFECT EXPOSUREOUTCOME INDEPENDENTDEPENDENT SMOKINGLUNG CANCER PROGRAMIMPACT DRUGCURE