T Value And Z Value. For a large sample size sample variance will be a better estimate of population variance so even if population variance is unknown we can use the z test using sample variance. Generally in elementary stats and ap stats you ll use a z score in testing more often than a t score.
As the data size increases distribution tends to be z distribution. Generally in elementary stats and ap stats you ll use a z score in testing more often than a t score. Here is a road map.
A z score and a t score are both used in hypothesis testing.
For a large sample size sample variance will be a better estimate of population variance so even if population variance is unknown we can use the z test using sample variance. Z scores are based on your knowledge about the population s standard deviation and mean. If the sample size is large enough then the z test and t test will conclude with the same results. Similarly for a large sample we have a high degree of freedom.
