For Z statistics we need population standard deviation while if population standard deviation is not known then sample size should be large (n>30) while for t statistics we need sample standard deviation with small sample size(n<30)
T distribution have longer Tail than Z statistics
T statistics have degree of freedom while Z statistics don't have degree of freedom.
If the population standard deviation is given then use Z statistics for testing of mean while
If the population standard deviation is not given but sample size is greater than 30 then use Z statistics with sample standard deviation.
While all questions related to proportion use Z statistics.
Get Answers For Free
Most questions answered within 1 hours.