Estimated St. Error
is an estimate of the st. error of the sampling distribution of the M.
Est. St. Error of the Sampling Dist of M
sample st.deviation / square root of n
t statistic is
formed whenever a statistic has a normal sampling distribution (M) is transformed by subtracting the mean of the sampling distribution and dividing by est of the st error (sample)
Comparison of t and z distrib
1. t and z both have means that equal 0
2. t and z both have distributions that are symmetric about the mean.
3. t dist are more variable than the z
4. Shape of a t changes with sample size
Degrees Of Freedom
is the number of degrees of freedom for a statistic equals the number of components in it's calculation that are free to vary. so, 1/5 are fixed and 4/5 are free to vary. n-1
a statistic is robust if it gives fairly accurate results even when an assumption is violated.
is used to locate power.
mue w.o st.deviation