1. Sumukh Deshpande n Lecturer College of Applied Medical Sciences Statistics = Skills for life. BIOSTATISTICS (BST 211) Lecture 2

2. Basic Data Analysis Process in Descriptive Statistics

4.  Is the data set a sample? Basic Data Analysis Process in Descriptive Statistics Yes RAW DATA "Filtered" DATA Nominal/Ordinal/Interval Range & Rank Data Is the data parametric ? No Sample/Population? N or n? s or  ? xbar or  ? Inspection: Outliers/missing values/other abnormalities SizeMeanSD Sample nX bars Population N 

5.  The odd ones out  Observations that are too large or too small.. (e.g a child 777cm tall)  They may be genuine!  Typing errors?  Other errors?  What should you do? Outliers 1 Yes RAW DATA "Filtered" DATA Nominal/Ordinal/Interval Range & Rank Data Is the data parametric ? No Sample/Population? N or n? s or  ? xbar or  ? Inspection: Outliers/missing values/other abnormalities

6.  Make note of outliers  Repeat analysis with and without outliers to show the difference  MISSING data is to be reported and investigated Outliers 2 Yes RAW DATA "Filtered" DATA Nominal/Ordinal/Interval Range & Rank Data Is the data parametric ? No Sample/Population? N or n? s or  ? xbar or  ? Inspection: Outliers/missing values/other abnormalities

7.  Before you perform analysis you must be comfortable with your data  Never remove outliers or add in missing data!  Assess and report. DO NOT ALTER RAW DATA “Filtered” Data Yes RAW DATA "Filtered" DATA Nominal/Ordinal/Interval Range & Rank Data Is the data parametric ? No Sample/Population? N or n? s or  ? xbar or  ? Inspection: Outliers/missing values/other abnormalities

8. Discrete Data

9.  Count your data. Check the size. N or n?  Rank the data min →Max or vice-versa  Work out the range Sorting your Data Yes RAW DATA "Filtered" DATA Nominal/Ordinal/Interval Range & Rank Data Is the data parametric ? No Sample/Population? N or n? s or  ? xbar or  ? Inspection: Outliers/missing values/other abnormalities Go to Excel ®

10. Ex1: KKH patients, 5 weeks  Is this data discrete or continuous? Week 1 1591231751991171279833 Week 2 1721361851001601187521 Week 3 17214516917618518091100 Week 4 1001171241781091048025 Week 5 1701041811991551568628 Why are these columns different?  Any outliers? Or missing data?

11. Ex2: school kids height  Is this data discrete or continuous? 134144138141136138142145 134138140 134136137 13913741144136138136132 142135136139142140134140 143134137144192141134141  Any outliers? Or missing data?

12. Ranking your Data using MS Excel  Put your data in ONE column, then select it all. Press

13. Frequency Tables & Charts

14. Frequency Tables 1 1. Rank your Data 2. Count how many times each observation appears 3. You have just made a FREQUENCY Table Xf 45324745324847 4548514732514548 Xf 323 454 474 483 512 16

15. Charts Using Excel 1. Charts help visualise data 2. Summarise information and facts 3. Easy to create with Excel 1. Charts are created from frequency tables 2. How to create a chart? 3. http://www.youtube.co m/watch?v=jLW1A7j7 r3Y http://www.youtube.co m/watch?v=jLW1A7j7 r3Y

16. Chart of the previous example Xf 323 454 474 483 512

17. Calculating Statistical Functions using MS Excel & Calculators Discrete Data

18. Stats functions Using Excel 1. Mean: =average(data range) 2. Median: =median(data range) 3. Mode: =mode(data range) 1. SD: =stdev(data range) 2. http://www.princeton. edu/~otorres/Excel/e xcelstata.htm http://www.princeton. edu/~otorres/Excel/e xcelstata.htm

19. 1. First go to SD mode 2. Clear memory 3. Enter data CORRECTLY 4. Visualise your data 5. Retrieve Statistical Functions Stats functions Using Casio fx-8nMS

20. 1. Selecting SD Mode

21. 2. Deleting Previous stats in memory

22. 3. Entering Data

23. 4. Visualising Data

24. 5. Retrieve Statistical Function

25. Practice Example  Calculate descriptive stats functions of the following data set using calculators, MS Excel and long hand calculation 55, 54, 51, 55, 53, 53, 54, 52 1. Start with long hand 2. Then Calculator 3. Finally use Excel

26. 1. Long Hand 1. Freq Table Mean, xbar = 427/8 = 53.375 427 n = 8 13.875 Variance = 13.875/(8-1)=1.98 SD =  Variance =  1.98 =1.41 55, 54, 51, 55, 53, 53, 54, 52

27. 2. Calculator 55, 54, 51, 55, 53, 53, 54, 52

28. 3. Excel 55, 54, 51, 55, 53, 53, 54, 52

29. All 3 routes led to the same answers Long Hand CalculatorExcel Mean53.38 SD1.41