# Exercise 4

```Exercise 4
NA1c0027
Q1:
1. Are the groups statistically different from each other on any of the tests?
What can you say about the precision of the estimates of mean difference (are
they precise or not very precise)?
Which test do you think has the largest effect size?
a:-1.57-0.99≒3
3/37≒0.081
b:-5.62-0.76≒6
6/200≒0.03
c:-10.8-(-0.01) ≒11
11/96≒0.114
C: The distance is the farthest. It doesn’t cover with zero.
Q2:
Are the groups statistically different from each other on any of the test?
What can you say about the precision of the estimates of mean difference,
given that the mean difference between groups’ PTP-NP is .42, the mean
difference between their OLP-NP is 3.38, and the mean difference between
their OLP-PTP is 0.14 ( are they precise or not very precise?
Which test do you think has the largest effect size?
OLP-PTP is the lowest effect side. Because the point distance between zero is the closest.
PTP-NP has the largest effect size, because its confidence interval has the largest
distance from zero. Meanwhile, OLP-NP has similar distance from zero.
Q3:
What do the confidence intervals tell you that p-values can’t?
The bigger the sample size the higher the power, the smaller the CI, the less sampling
error, the more precise and certain the statistic as an estimate of the parameter effect
sides. Confidence intervals not only tell us if the task is statistic significant or not ( if
the confidence interval covers zero or not), it offers the same function as p-values do.
```