Tests of Significance: How to Remember?

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  • Step 1: First look at the type of variable. Is it quantitative or is it qualitative variable?
    • Quantitative variable: Can be measured and expressed as ‘mean’ (Ex: Number of children, Height, Weight, mean Hb% etc.)
    • Qualitative variable: Cannot be measured but expressed in ‘proportion’ (Ex: Blood group, Severity of anemia, Prevalence of obesity etc.).

 

  • Step 2: See how many groups are discussed in the question. It may be:
    • Comparison between 2 groups
    • Comparison within 1 group: before & after an intervention.

 

  • Step 3: Give the answer by following the table:

Tips to remember:

  • ‘Quanti’ contains 1 T: So, in ‘Quanti’ variables: T test to be done
    • If done between 2 groups: the test of choice is Student’s T test (as the word ‘STUDENT‘ contains 2T)
    • If done among >2 groups: test of choice is ANOVA (Remember: QUANTITATIVE – ANOVA)
  • If variable is qualitative and done¬†between 2 groups: the test of choice is Chi-Square as ‘Square’ means 2nd power.

 

Example 1:

The prevalence of DM was 20% in a population. After an awareness campaign of impact of diet on DM, it came down to 13%. Which test of significance should be used?

  1. Chi-Square test
  2. McNemar test
  3. Student’s T test
  4. Paired T test.

Explanation:

  1. Step 1: Type of variable: Prevalence of DM: Qualitative variable
  2. Step 2: Only 1 group: Before & after an intervention
  3. Step 3: So, the test of choice is McNemar test.

 

Example 2:

Mean Hb level in a group of adolescent women was 9.2 gm%. After iron & folic acid tablet supplementation, it goes to 9.6 gm%. Which test of significance should be used?

  1. Chi-Square test
  2. McNemar test
  3. Student’s T test
  4. Paired T test.

Explanation:

  1. Step 1: Type of variable: Mean Hb levele: Quanti-tative variable (T test)
  2. Step 2: Only 1 group: Before & after an intervention
  3. Step 3: So, the test of choice is Paired T test.

Example 3:

Mean Hb level in 3 groups of adolescent women was 9.2 gm%. After iron & folic acid tablet supplementation, it goes to 9.6 gm%. Which test of significance should be used?

  1. Chi-Square test
  2. Student’s T test
  3. Paired T test
  4. ANOVA test.

Explanation:

  1. Step 1: Type of variable: Mean Hb levele: Quantitative variable
  2. Step 2: 3 groups involved
  3. Step 3: So, the test of choice is ANOVA test (QUANTITATIVE – ANOVA).

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