Confidence Intervals for Means & Proportions Flashcards
What is the standard deviation?
A measure of how dispersed the data is related to the mean
If distribution is normal….
Mode=median=mean
Mean and standard deviation characterize what?
Distribution of the sample
Sample mean?
The mean of the sample; a statistic
Pop. Mean?
Mean of the population; parameter
What is 1 standard deviation?
68%
-add and subtract 1 from the mean
What’s 2 standard deviations?
95%
-add and subtract 2 from the mean
Central limit theorem?
Allows us to infer a prameter from a stat
Ex: if we want to know about the average age of Hispanic men who smoke. We carefully gather one sample and infer it
Standard error?
Same as SD but w/ a distribution of the mean
Standard error (SE)?=
Standard deviation / sq root of the # of samples
What happens w/ a slight skew?
The mean is pulled from the mode w/ the median in between
-the greater the skew, the more the mean is pulled away
Formula for CI? Terms?
Vvv
Inference?
to make claims about a pop. based on a statistic
- sample means~pop means
- sample standard deviations~ pop. standard deviations
- sample proportions~ pop. proportions
How to compute the stantard error (SE)?
S/sq root of sample size
Look at slide 15
Standard error (SE)?
Measures the accuracy in which a sample distribution represents a population with the standard dev.
-Formula: sample standard deviation/ sq root of sample #
