Chapter 6 Flashcards
What is the Standard Error?
SE = s/sqrt(n)
What does the standard deviation describe and what does the standard error describe? (lamb birthweight example)
Standard Deviation - the variability of birthweights among lambs in the sample
Standard Error - the variability associated with the sample mean viewed as an estimate of the population mean
What is the formula for a 95% confidence interval?
What does the t distribution depend on?
degrees of freedom
When can you use the Student’s t distribution?
is the data is distributed normally
How can you determine which confidence interval is wider?
the one with greater percent confidence
What does the confidence interval mean say for 95%?
-if we calculate 100 different 95% confidence intervals we expect that for about 5 of these the mean will not be contained in the interval
How do we take one sided confidence intervals?
with infinity (20, infinity) or (infinity, 70)
What three things are needed for confidence interval strategy to work?
-a simple random sample
-every member of the population has the same chance of being included in the sample
-the members are chosen independently of one another
If the sample size is small for the confidence interval to work what must the distribution be?
approximately normal
