Stat Tests: Purpose, degrees of freedom and Null hypothesis

Question 1

Standard deviation

Answer 1

Purpose: Measures the spread of data from the mean. Outside 2 s.d. from mean = anomaly

Question 2

Unpaired student t-test

Answer 2

Purpose: used to compare 2 means (from different individuals) and test for significant difference between them.

Degrees of freedom: (1n + 2n) -2

Null hypothesis: no significant difference between means

Question 3

Paired student t-test

Answer 3

Purpose: used to compare 2 means (from the same individual) and test for significant difference between them

Degrees of freedom: n-1

Null hypothesis: no significant difference between means

Question 4

Spearman’s Rank

Answer 4

Purpose: used to assess the relationship between 2 sets of data and indicate if they are correlated or not (if there is a linear correlation between them)

Degrees of freedom: none (critical values)

Null hypothesis: There is no relationship between 2 sets of data

Question 5

Chi Squared

Answer 5

Purpose: Chi-squared is used to observed frequency fits the frequency you expected or predicted

Degrees of freedom: n-1

Null hypothesis: There is no statistically significant difference between the observed frequency and the expected frequency