POP Sampling

Question 1

CI significance

Answer 1

If CI includes 1, not significant.
If CI does not include 1, significant.

Question 2

Using 95% CI to determine difference between trial groups.

Answer 2

If the 95% CI includes 0, there is no difference between trial groups.
If the 95% CI does not include 0, this is a difference between trial groups and a p value can be calculated to work out whether this is due to chance or another factor.

Question 3

Interpreting p values

Answer 3

• If <0.05, probability of observed difference due to chance alone is small – statistically significant [reject the null hypothesis & accept the alternative hypothesis].
• If >0.05, probability of observed difference due to chance alone is large – statistically insignificant (no evidence of an effect) [reject the alternative hypothesis & accept the null hypothesis].

Question 4

Null hypothesis vs Alternative hypothesis.

Answer 4

Null hypothesis – no difference in the population.
Alternative hypothesis – a difference in the population.

Question 5

Type I vs Type II Errors.

Answer 5

Type I error – no difference, but the test says there is (i.e., false positive).
Type II error – there is a difference, but the test says not (can challenge this error by increasing the population sample size) (i.e., false negative).

Question 6

Negatively vs positively skewed.

Answer 6

Negatively (left) skewed - Mean < Median < Mode
Positively (right) skewed - Mode < Median < Mean.