Unit 9: Standard errors and inferences Flashcards
the difference between a sample statistic and a population that is due to chance is referred to as
sampling error
a sampling distribution of the sample mean is based on taking repeated samples of size n from the same population and plotting the () of the different samples
mean
how do we notate the sample means
m of mu
if enough samples are taken, it will equal the population mean
how do we denote the standard deviation of the sample means
the standard error of the mean (S.E.)
the standard deviation of the sample means
as n increases, SE of M decreases
if you dont have the population standard deviation you can use the sample’s
standard error
A type of standard deviation
* A measure of the precision of sample mean
* Helps indicate the uncertainty around the estimate of the mean
measurement (more about that next week)
* Tells us how close/precise we are to the population mean
standard deviation
describes the variability between individuals in a sample
standard error of the mean
describes the uncertainty of how the sample mean represents the population mean
what’s the issue with conflating sd and sem
the sem is always less than the sd so it misleads the reader into underestimating the variability between individuals within the study sample
sem is a type of sd- it doesnt tell you the dispersion, it tells you how precise your estimate may be to the population
Just like standard deviation, standard error is a measure of variability. However, the difference is that standard deviation describes variability within a single sample, while standard error describes variability across multiple samples of a population
descriptive stats examples
mean, sd, min, max, etc
error bars
that’s where descriptive and inferential stats are mixed together
if you want to showcase distribution and spread of data what graphs do you use
boxplot or histogram
if youre illustrating potential differences between groups
bar plots
bar plots with error bars
what does it mean if error bars overlap
When the error bars overlap,
the means represented by the
two bars are probably not that
different.
what does it mean if error bars dont overlap
When the error bars don’t
overlap, they may or may not
be that different.
