1. Research Methodology
Lecture No :25 (Hypothesis Testing – Difference in Groups)

2. Recap Goodness of data is measured by reliability and validity.
Three measures of central tendency: mean, median and mode.
Dispersion is the variability.
Three measures of dispersion are: range, variance and standard deviation.
Correlation
SPSS Cronbach Alpha (Reliability) Factor Analysis (Validity)

3. Hypotheses Testing Difference between groups
Relationship between variables

4. Types of Hypotheses Null
that no statistically significant difference exists between the groups
No Statistically significant relationship exists between variables
Alternative
logical opposite of the null hypothesis
that a statistically significant difference does exist between groups
That statistically significant relationship exists

5. Choose Appropriate Tests
Based on the number of variables
i.e. two variables relationship (Univariate)and
many variables (Multivariate) statistical techniques.
The type of scales Nominal, Ordinal(Non Metric) , Interval and Ratio(Metric) used choose appropriate tests
See page 338 of the text book.

6. Computer Outputs
See the output results of the computer generated outputs indicating the significance level.

7. Testing for Statistical Significance
State the null hypothesis
Choose the statistical test
Select the desired level of significance
Compute the calculated difference value
Obtain the critical value
Usually the software now provides the standard significance values and the f or t values. Based on the significance level value one can interpret the test
Interpret the test

8. Selected Group Difference Cases
Testing single mean
Testing two related means (ratio)
Testing two related samples when data is in ordinal / nominal
Testing two in unrelated means
Testing when more than two groups on their mean scores

9. Testing a hypothesis about a single mean
One sample t test
Mean of the population from which a sample is drawn is equal to comparison standard.
i.e. we known that the in general the students on an average study for 32 hours.
Now you want to test that the students at V-CIIT which are part of the student population study less.

10. So the sample of V-CIIT differ from the rest of the population needs to be tested.
Hypothesis generated would be
Ho: The number of study hours of students V_CIIT is equal to the number of hours studied in general.(same)(no difference)
Ha: The number of hours students of V_CIIT is less then the number of hours studied in general (< )

11. SPSS
Analysis Compare means  One sample T Test.
Say you set the significance level to then
See the output results of generated from the software. See if the differences are significant or the relationship significant. (lecture 6-7)
If the differences are not significant then we accept the null hypotheses other wise accept the alternate
Out Put (T value and significance level)

12. Testing hypotheses about two related means
Paired samples t-test
Examine the difference in the same group before and after the treatment
Performance before training and after training
Two observation each employee
Null hypothesis
There is no difference between the performance of before and after the training

13. SPSS
use pair t test and see the value of t and it’s significance level
If the differences are not significant then we accept the null hypotheses other wise accept the alternate
Meaning the before and after training there was no change i.e. Null hypothesis is accepted
There is no difference between the performance of before and after the training

14. Non Parametric Test for paired sampled
When population cannot be assumed to be normally be assumed distributed
Use Wilcoxon singed –rank test ,
Use McNemar’s test for non parametric and nominal data

15. Testing about two unrelated means
Group difference when groups are not related and variable of interest data is in interval and ratio scales.
E.g: Groups MBA and Non MBA compared on sales achieved.
SPSS Analyze  Compare means Independent samples T Test
If more than two groups use ANOVA ( sales by different level of education(Metric, FA, BA/BS,Masters )

17. SPSS excercises