Stats reviewer

Created by

Mia Ayala

Cards (20)

Estimate
is the value of range of value, that approximates the population value
Point Estimate
Is a specific numerical value of a population parameter. The sample mean X is the best estimate of a population mean
Interval estimate
Also called as confidence interval, is a range of values used to estimate a parameter.
Confidence level
Is the probability that the interval estimate will contain the trues population parameter.
Critical value
Also known as confidence coefficient, are the z-values that is used in describing the characteristics of a target population. When (PSD) is known, z-values are used.
90% confidence
z = ±1.65
95% confidence
z = ±1.96
99% confidence
z=±2.58
formula
Margin of error formula
Interval estimate is expressed as
Lower limit (X-E<mean<X+E) Upper Limit
Degrees of freedom (df)
are the numbers of values that are free to vary after a sample statistics has been computed.
Degrees of freedom formula
df=n-1
Margin of error formula when PSD are unknown
E=t(s/√n)
Interval estimate expression when sd is unknown
(X-E˂µ˂X+E)
T distribution
Is a probability distribution that is used to estimate population parameters when the sample size is small and/or the population variance is unknown.
T distribution
Was developed by William Sealy Gosset in 1908
Formula of t distribution
$t=$ $¯x−μ/s/√n$
When will we use the formula of t distribution?
When n<30 and the population standard deviation is unknown
Properties of t distribution
Is symmetrical about 0
Is bell shaped like normal distribution but with heavier tails
The mean, median, and mode is equal to 0
The variance is always greater to 1. It is equal to v/v-2 where v is the number of degree of freedom
As the df increase, the curve looks more and more like the normal distribution
The standard deviation of t distribution varies with the sample size
The total area under at t distribution curve is 1 or 100%
Formula of variance
V/v-2
Where v is df