Confidence Intervals Flashcards
What are the two types of statistical inference methods?
Estimation of population parameters and testing hypotheses about the parameter values.
What is a point estimate?
A single number that is our best guess for the parameter
What is an interval estimate?
an interval of numbers within which the parameter value is believed to fall.
Why is a point estimate alone not sufficient?
It doesn’t tell us how close the estimate is likely to be a parameter
What two properties does a good estimator have?
A sampling distribution that is centred at the parameter, this is said to be unbiased. It also has a small standard deviations compared to other estimators.
What is a confidence interval?
An interval containing the most believable values for a parameter.
What is a confidence level?
The probability that a confidence interval produces an interval that contains the parameter.
What is the margin of error?
Measures how accurate the point estimate is likely to be in estimating a parameter
What two factors effect the margin of error
Margin of error decreases as the sample size increases and increases as confidence level increases
What constitutes as a large sample for the 95% confidence interval p+/- 1.96(se)?
15 successes and 15 failures
What do % interval methods assume about the data?
Obtained by randomisation and large enough sample n that there are 15 successes and 15 failures.
How does a t score differ from a z score in terms of the curve?
The tails are a bit thicker in the t distribution
df =
n-1
using a tscore to construct a confidence interval requires
randomly obtained data and an approximately normal distribution
When is a statistical method said to be robust?
It is said to be robust to a particular assumption if it performs adequately even when that assumption is moderately violated. (normal distribution of tscore.)
