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# 7.sampling fundamentals

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### 7.sampling fundamentals

1. 1. SamplingfundamentalsD.A. Asir John Samuel, MPT (Neuro Paed), Lecturer, Alva’s college of Physiotherapy, Moodbidri Dr.Asir John Samuel (PT), Lecturer, ACP
2. 2. Some fundaments definitions• Population- Collection of all the units that are of interest to the investigator• Sample- Representative part of population• Sampling- Technique of selecting a representative group from a population Dr.Asir John Samuel (PT), Lecturer, ACP
3. 3. Some fundaments definitions• Sampling error- The difference that occurs purely by chance between the values of sample statistic and that of the corresponding population parameter Dr.Asir John Samuel (PT), Lecturer, ACP
4. 4. Need for sampling• Only feasible method for collecting information• Reduces demands on resources (time, finance,.)• Results obtained more quickly• Better accuracy of collected data• Ethically acceptable• Only way when population contains infinite members Dr.Asir John Samuel (PT), Lecturer, ACP
5. 5. Sampling distributions• Parametric tests• Non parametric tests Dr.Asir John Samuel (PT), Lecturer, ACP
6. 6. Chi-square Test (x2)• Variables of interest are categorical (quantitative)• To determine whether observed difference in proportion b/w the study groups are statistically significant• To test association of 2 variables Dr.Asir John Samuel (PT), Lecturer, ACP
7. 7. Chi-square Test-Assumption• Randomly drawn sample• Data must be reported in number• Observed frequency should not be too small• When observed frequency is too small and corresponding expected frequency is less than 5 (<5) – Fischer Exact test Dr.Asir John Samuel (PT), Lecturer, ACP
8. 8. Test statistic x2 = ε(O-E)2/EO – observed frequencyE – expected frequency Dr.Asir John Samuel (PT), Lecturer, ACP