review Flashcards
(22 cards)
whats important about stats
the focus is in the long run
fact
its impossible to know the population exactly unless we have all of the data points
how many possible samples could there be
numerous
does stats guarantee our guess is free of mistakes in a sample
no it only guarantees on average no mistakes in the long run
stats is not about how well we guess in a certain sample
it is about our overall performance in all the possible samples.
point estimation
-use a specific value to estimate the population parameter
sample mean—->
population mean
(2,2,2,6,8) best guess of the population mean?
4 because thats the mean of that sample
one type of interval estimation
-confidence interval
estimation
a range of plausible values for μ
death comparison
you are either 100% dead or 100% alive
confidence interval formula
68% (mean - 1 xSE, mean +1 xSE)
central limit theorem
in the population, if data follow a normal distribution, then the sampling distribution of sample means is a normal distribution too
standard error formula
standard deviation over sample size (n) squared root
distribution of incomes in the population
positively skewed
distribution of incomes within a certain sample of 1000 families
positively skewed
distribution of the average incomes of all the possible samples
approximately normal
standard error
just a special type of standard deviation
what does standard deviation do
measures variability
what happens when the sample size is larger
the more stable x (mean) is and the more unlikely to see extreme x (mean) values
sampling error
- children look like their parents but they don’t look exactly the same
- look slightly different
random sampling
-ensures they look similar
