This document defines statistics and describes its uses in medical research. Statistics is the science of dealing with numbers to obtain objective, unbiased information from data. In medicine, statistics is used to descriptively summarize population data, prove associations between variables, compare study groups, and evaluate health programs. Data comes from records, surveys, and research studies. Statistical analysis involves collecting, summarizing, and presenting data in tables and graphs, then interpreting the information. Inferential statistics tests hypotheses using significance tests for means, correlations, regressions, and distributions to analyze relationships between variables and predict outcomes. Correlation does not necessarily indicate causation. Qualitative data is also analyzed using chi-squared and difference of proportions tests.

1. STATISTICAL METHODS

2. Medical Statistics
Prof.Dr.Amany Rashad Aboel-Seoud
Community Medicine Department
Zagazig university

3. Definition of statistics
• It is the science and art of dealing with
numbers.
• Used for collection, summarization,
presentation and analysis of data to get
information based on objective basis (un-
biased).

4. Uses of statistics
• Descriptive information for any
population
• Prove association between variables
• Prove relation between risk and disease
• Compare two studied groups (or more)
• Evaluate health programs & services

5. Medical Statistics
STATISTICAL
ANALYSIS
useful
INFORMATION
In medical field
DATA
(accuracy)

6. DATA
SOURCES
Records, Census
Survey, Research studies
(sampling)
PRESENTATION
Tables
Summarization
Graphs
Analysis &
interpretation
information
Planning for health programs

8. population

15. Inferential Statistics
• Put a hypothesis
X = Y H0 or X >Y H1 or Y>X H2
• Collect, summarize data
• Test your hypothesis using tests of significance:
Comparison of mean values : t , paired t test & ANOVA
(used for numeric continuous data)
Finding relations between different variables using
Correlation & regression tests

23. Correlation test
To find a relation between 2/more variables in
direction & strength (one is dependent =
response. It is plotted on the y axis) &(the
other/s is independent = explanatory or risk. It is
plotted on the x axis)
• Correlation does not mean causation.
• Spurious correlation: significant statistically but
insignificant clinically

25. Types of correlation
+ve
-ve
No

26. Coefficient of correlation “r” ranges from 0 to 1 It is
either +ve or -ve in direction
(r=0.5 p=0.02), (r=- 0.6,p=0.01) (r= 0.1,p=0.98)
Coefficient of determination R 2 : to quantify the variation of
one variable that is contributed to the other variable.
Types of correlation:
I) single (simple) & multiple
II) Pearson : numeric, normally distributed, linear
Spearman : ordinal, non linear, not normally distributed

27. Regression analysis
To predict a dependent variable from another known
variable (s).
• Linear: dependent = intercept +/- b coefficient x
independent variable
e.g. birth wt = y +/- b x gestational age
= 0.21 + 5 x 36
• Multiple
e.g. Birth wt= y +/- b1*gest+/- B2*HC

43. Wilcoxon test, Mann Whitney test

48. Analysis of qualitative data
(1) Chi squared test : to find significant relation
between 2 variables or order distributions or
categorical data.
(2) Difference between proportions (z test)
as t test but use percentage instead of mean
values

65. Thank you