Dr. Mona Hassan Ahmed Hassan - PowerPoint PPT Presentation

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Dr. Mona Hassan Ahmed Hassan

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Minitab 10 Statistica 9 Excel 8 MedCalc 7 S-PLUS 6 SUDAAN 5 Epi Info 4 STATA 3 SPSS 2 ... File in SPSS Data Entry Slide 23 Data cleaning Simple frequency ... – PowerPoint PPT presentation

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Title: Dr. Mona Hassan Ahmed Hassan


1
  • Dr. Mona Hassan Ahmed Hassan
  • Prof. Biostatistics

2
Computer Utilization
for Diabetes Epidemiology
3
Statistical Software
What to do before sitting to PC?
How to generate and interpret results?
Objectives
4
Data Coding
  • Transformation of qualitative information into
  • Numbers
  • OR
  • Symbols

5
Data Preparation
Either the information is transferred from the
original record to a coding sheet
Ser. Ser. Ser. Ser. Ser.  Ser. 
Column Code Column Code Column Code
Age Age Age
Sex Sex Sex
MS MS MS
Educ.
Coding form
6
Code
1
10/01/2008
25/08/1986

f
1

160
58
  • ID 1
  • 1. Date of Interview
  • 10/1/2008
  • 2. What is your date of Birth?
  • 25/8/1986
  • 3. What sex are you?
  • Male (m) Female (f)
  • 4. What is your marital status?
  • Single (1) Married (2)
  • Widowed (3) Divorced (4)
  • 5. What is your height (cm)?160
  • 6. What is your weight (kg)?58

7
Coding by more than one person
  • Precise instructions should be developed for
    coders
  • Coders, must be trained
  • check for inter-coder reliability


8
Sorting of the questionnaires
101-200
1-100
9
  • Describing the Sample
  • measures of central tendency and variability. 
  • The appropriate measure of central tendency and
    variability will depend upon the variables level
    of measurement and the shape of the distribution. 

10
Scales of measurement
11
Scales of Measurement
Ali
Ramy
Samy
Nominal Symbols Assigned to
Runners Ordinal Rank Order of
Winners Interval Performance Rating on a
0 to 10 Scale Ratio Time to Finish, in
Seconds

Finish
Finish
3
7
9
15.2
14.1
13.4
12
Scales of Measurement
13
Shapes of Distribution
Mean Median Mode
68 within meanSD 95 within mean2SD 99 within
mean3SD
14
Right-skewed distribution
Mode Median Mean
  • If Mean gt Median ? Positive or right skewness

  • (long right tail)
  • It arises when the mean is increased by some
    unusually high values

15
Left-skewed distribution
Mean Median Mode
  • If Mean lt Median ? Negative or left skewness
    (long left tail).
  • Negative skewness occurs when the mean is reduced
    by some extremely low values.

16
Inference
  • Developing and Testing a Hypothesis
  • differences in frequency distributions of nominal
    level variables  chi-square
  • associations or correlations between variables, 
    bivariate correlations  
  • differences between groups with respect to the
    distribution of interval/ratio level data. t-tests

17
The most popular statistical packages
1 SAS
2 SPSS
3 STATA
4 Epi Info
5 SUDAAN
6 S-PLUS
7 MedCalc
8 Excel
9 Statistica
10 Minitab
Sample size
18
Using Epitable (Under EpiInfo) to Calculate
Sample Size
19
(No Transcript)
20
SPSS
Statistical
Sciences
Packages
Social
FOR
21
Creating a Data File in SPSS
  • ID
  • Gender Male Female
  • Date of Birth
  • Educational Level (years)
  • Employment Category 1 Clerical 2 Custodial 3
    Manager
  • Current Salary
  • Beginning Salary
  • Months since Hire
  • Previous Experience (months)
  • Minority Classification 0 No 1 Yes

22
Data Entry
  • Excel
  • Access
  • Word
  • Any Statistical software

23
Data entry
24
Data cleaning
  • General data check
  • Printout
  • Quick data check (Frequency tables)
  • 1- Wild codes check (invalid codes)
  • 2- Completeness check ensure that
  • all cases collected are
  • represented in the data file
  • without replication

25
Simple frequencyData check
26
  • Perform Descriptive Statistics

27
Descriptive
28
(No Transcript)
29
Conduct Simple Correlations and regression
30
Correlation

31
Regression

32
Scatter
33
t- test (Two independent groups)
34
t- test (Two independent groups)
35
t- test (Two independent groups)
36
Paired t- test (Dependent groups)
37
Chi-Square test
38
Thank You
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