Preparing to Analyse Data C.Adithan Department of Pharmacology JIPMER Pondicherry

NominalProportion Categorical OrdinalScores, Ranks Continuous NumericalInterval Discrete Types of Data Categories of Measurement

Nominal scale: e.g., Male, Female Hindu, Muslim, Christians - Expressed in proportions (60% male, 40% female) Ordinal scale: e.g., Mild, Moderate, Severe pain Light, average, heavy, very heavy smokers - Expressed as Scores and Ranks Data can be arranged in an ORDER and RANKED

Interval/Ratio scale:  Highest order of the measurement  Assume equal intervals in its measurement Interval scale: - Does not have an absolute zero point e.g., Temperature on the centigrade scale Ratio scale: - Has an absolute zero point e.g., blood sugar For Statistics Interval and Ratio Scales are treated as SAME

Analysis of Data: Consider 4 specific aspects  Checking of Data  Missing Data  Outliers - Affect Mean  SEM; Regression analysis  Transformations - logarithmic - Square root - reciprocal

Outlier r value With outlier: 0.65 Without outlier : 0.07

Summary Statistics:  Arithmetic mean  Mode  Median  SD  SEM  Proportion  Confidence Interval (C.I.)

Measures of Central Tendency  Arithmetic mean: Sum of all values divided by Number of observations  Mode Most common value observed  Median Value that comes half-way when the data are ranked in order Mean= 28/7 = 4, Mode=5, Median=

Measures of Dispersion  Range: Difference between lowest and highest scores in a set of data  SD: describes the variability of observations about the mean  SEM: describes the variability of means 80, 70, 80, 5, 2, 3,1 Range=80-1=79 80, 6, 7, 30,12, 2,1 Range=80-1=79 80, 70, 80, 5, 2, 3,1 S.D.= 34.4 ± , 6, 7, 30,12, 2,1 S.D.= 19.7 ± , 70, 80, 5, 2, 3,1 SEM= 34.4 ± , 6, 7, 30,12, 2,1 SEM= 19.7 ± 10.7

Measures of Dispersion Confidence Interval Describes the limit within which 95% of mean values, if determined in similar experiments are likely to fall Lower limit = mean – (t 0.05 x SEM) Upper limit = mean + (t 0.05 x SEM) 80, 70, 80, 5, 2, 3,1 95 % C.I. = 34.4 (-2.2, 71.1) 80, 6, 7, 30,12, 2,1 95 % C.I. = 19.7 (-6.5, 45.9)

Rounding of Numbers