Exam 2: My Notes Flashcards
Symbols for means and standard deviations for samples or populations
μ = population mean
σ = population standard deviation
X ̄ = sample mean
s = sample standard deviation
Mean(X ̄ )= mean of the sampling distribution of X ̄
SD(X ̄ )= standard deviation of the sampling distribution of X ̄
Why do we care about sampling distributions?
Assess uncertainty of sample results
If we know the spread og the sampling distribution (standard deviation) we would know how far our x-bar might be from the the true μ above or below
Why is the sampling distribution important
If a sampling distribution has a lot of variability, then if you take another sample it’s likely you’ll get very different samples
About 95% of the time the sample mean will be within 2σ/sqrt(n)
It tells us how close the sample statistic should be to the population parameter
Why is the normal distribution so important in the study of statistics
The Central Limit Theorem - The sampling distribution of a statistic often follows a normal distribution if the sample sizes are large enough
How do we use the Statistical Process Control?
Use statistical paradigm to monitor process variables (input, output, etc.) over time.
Decide if variability is consistent and within limits
Variable vs. Parameter
variable - What is actually being measured on each subject
parameter - Overview of the data, summarizes the variable, about population
