- What is meant by confidence interval in data analysis e.g. 95% confidence interval?
- How does p<0.05 estimate significant difference?
David Quinn answered for the first point: the data have a 95% probability to be in the interval.
I am not sure to understand the second question. I assume that you speak of the p-value. The p-value is the result of an hypothesis test: it is the probability that the data are what they are if the null hypothesis is true.
Imagine that you have two sets of numbers, generated by unknown random processes, and you want to know if the difference between the averages of the two sets is statistically significant.
You perform an hypothesis test where the null hypothesis is that both random processes have the same mean. If your p-value is less than 5%, it means that given your two sets, there is less than 5% probability that both random processes have the same mean. So you can say that the difference of average between the two sets of numbers is statistically significant.
- An interval, based on a sample, which has a $95$% probability of containing the unknown population parameter. Note that the interval is variable, but the unknown parameter is fixed.
- Not sure what you mean. the word "significant" is used to describe the p value of 5%, just like "highly significant" is associated with a p value of 1%.