Data Collection, Data Analysis, sample size calculation https://www.youtube.com/watch?v=-NMr6KuUKEQ

1. 1

2. Sample size
calculations
Dr. Mohamed M. Omran
Associated prof. of Biochemistry
Biochemistry department
Faculty of science
Helwan University
Bio-statistical
analysis
in Clinical
Research
Sample size
calculation

3. Outlines
1. What is biostatics?
2. Types of data variables
3. Data inputs
4. Normal distribution
5. P value
6. Biostatics tests
7. 95 % confidence interval
8. Correlation
9. Diagnostic performances
10. sample size calculation

11. The null hypothesis that there is no significant difference
between specified populations, any observed difference being
due to sampling or experimental error.

14. P Values • The probability that any observation is
due to chance alone assuming that the
null hypothesis is true
• Typically, an estimate that has a p
value of 0.05 or less is considered
to be “statistically significant” or
unlikely to occur due to chance
alone.
• The P value used is an arbitrary
value
• P value of 0.05 equals 1 in 20
chance
• P value of 0.01 equals 1 in
100 chance
• P value of 0.001 equals 1 in
1000 chance.

15. Normal distribution
(when group individuals less than 30 )
• Most of the biological variables usually cluster around a central value, with
symmetrical positive and negative deviations about this point. The standard
normal distribution curve is a symmetrical bell-shaped.
• In a normal distribution curve, about 68% of the scores are within 1 SD of the
mean.
• Around 95% of the scores are within 2 SDs of the mean and 99% within 3 SDs
of the Mean.

17. Parametric
Non- Parametric

18. Comparison between parametric and nonparametric tests

22. One way ENOVA
1. Bonferroni is the powerful tests
(Equal and non equal groups)
2. Tukey (equal groups)
3. Scheffe (unequal groups)

23. McHugh, M. L. (2011). Multiple comparison analysis testing in ANOVA. Biochemia
medica: Biochemia medica, 21(3), 203-209.

27. Comparing the two
OR and RR are usually
comparable in magnitude
when the disease studied is
rare (eg, most cancers).
However, an OR can
overestimate and
magnify risk, especially
when the disease is more
common (eg, hypertension)
and should be avoided in
such cases if RR can be
used
https://www.mappingccs.com/biostatistics

28. Correlation

30. Correlation

31. Statistical box plot
Box plots graphically depict numerical data using their descriptive statistics,
0 Mean extreme value , must delete ; * outline value, not delet

32. Evaluation of
diagnostic
performances
of markers
AUC equal to 1.0 is
characteristic of an
ideal test, whereas 0.5
indicates a test without
diagnostic value. The
nearer a curve shifts to
the top left and corner
of the graph, the more
useful the marker is for
the diagnosis.
Receiver Operating Curve
(ROC), Sensitivity , Specificity
Positive predictive value (PPV)
Negative predictive value
(NPV)

33. COVID-Ag
COVID-Ag

34. https://www.medcalc.org/calc/diagnostic_test.p
hp

38. Editor and reviewer
comments shock
Insufficient sample size
!!!!!!!!!

40. What do
you need prior
to sample size
calculation?

46. Software used for sample size calculation.
• Calculation of sample size by medcalc
• https://www.medcalc.org/manual/sampling_menu.php

47. For TNF The minimal sample size is 68,
(34/group)To have a power of 80% to assess
whether the TNF is significantly higher in HCV-
HCV of ~20.4 (11.6) compared to HCV ass
significant fibrosis ~12.6 (11), using a 2
samples means test and a significance level of
0.05
Sample size for difference between
two independent means.

48. Anther example
• For Il10The minimal sample size is
178 (89 per group)To have a power of
80 % to assess whether IL-10 is
significantly lower in HCC (of ~14.2
(13)) compared to patients with
significant liver fibrosis... (19.7 (13)),
using a 2 samples means test and a
significance level of 0.05

49. Sample size
calculation
using ROC

50. Sample size calculation using ROC

51. Sample size for sensitivity & specificity.
For calculation sensitivity , for a marker for example 70 , CI = 10, sample is 123

52. Sample size for correlation analysis.

53. Sample size reporting.