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220113P - INFERENTIAL STATISTICS FOR DISCRETE DATA

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Presented at the Research Methodology Winter Camp of AlMaarefa University on January 13, 2022 at 10.00am by Omar Hasan Kasule MB ChB (MUK), MPH (Harvard), DrPH (Harvard) Professor of Epidemiology and Bioethics

 

INTRODUCTION:

  • The inference is drawing conclusions on the relation between the independent and dependent variables.
  • Inference on discrete data is based on the binomial/multinomial distribution.
  • The analysis is essentially a comparison of proportions between 2 groups or among several groups.
  • There are more advanced methods not based on proportions that are covered by more advanced courses.

 

STATISTIC USED:

  • It uses 2 approximate methods (z-statistic and the chi-square) used for large samples and one exact method (Fisher's Exact Method) used for small samples.
  • Approximate methods are accurate for large samples and are inaccurate for small samples.
  • There is nothing to prevent exact methods from being used for large samples.
  • The commonest method is the chi-square method and is the one we shall describe.

 

STEPS:

  • State the null and alternative hypotheses in terms of proportions.
  • Ascertain the normal distribution of the data, equality of variances of sample proportions being compared, and adequacy of the sample size.
  • The data is laid out in contingency tables and is inspected manually before the application of statistical tests.
  • Use technology (SPSS) to compute the chi-square and derive the p-value.