Midterm 2 Flashcards
What is variance?
a statistical measurement of the spread between numbers in a data set
What does variance mean?
variance is the expected value of the squared deviation from the mean of a random variable.
How is variance interpreted?
Variance tells you the degree of spread in your data set.
What is standard deviation?
a measure of the amount of variation of the values of a variable about its mean.
What are Z scores?
the number of standard deviations by which the value of a raw score is above or below the mean value of what is being observed or measured.
How are z scores interpreted?
A positive Z-score shows that your value lies above the mean, while a negative Z-score shows that your value lies below the mean
What are the qualities of normal distribution?
symmetric, unimodal, and asymptotic, and the mean, median, and mode are all equal.
What is sampling error?
A statistical error that occurs when an analyst does not select a sample that represents the entire population of data
What effect does sampling error have on data?
Large sampling errors can lead to incorrect estimates or inferences made about the population based on statistical analysis of that sample
What is standard error?
a statistic that reveals how accurately sample data represents the whole population
How is standard error estimated?
calculated by dividing the standard deviation by the sample size’s square root
What does central limit theorem say?
the sampling distribution of the mean will always be normally distributed, as long as the sample size is large enough.
Why is central limit theorem relevant?
it allows one to assume that the sampling distribution of the mean will be normally distributed in most cases.
What are confidence intervals?
a tool for estimating a parameter, such as the mean of a population.
What is the proper interpretation of confidence intervals?
describes the uncertainty inherent in this estimate, and describes a range of values within which we can be reasonably sure that the true effect actually lies.
What is confidence?
another way to describe probability
What is t-distribution?
a continuous probability distribution that generalizes the standard normal distribution.
What is degrees of freedom?
the number of values in the final calculation of a statistic that are free to vary.
Formula of mean
m = sum/number
Formulas for z scores
z= x-mean/sd
Formula for Interquartile range
IQR = (Q3) - (Q1)
Formula for standard error
SE=SD/√N
Formula for margin of error using z
MOE= Z x SD/√N
