What is the difference between a t-statistic and a z-statistic?

I have been studying hypothesis testing for several weeks now and one thing that I have learned is that when it comes to hypothesis testing, it is important to use the correct statistical measure, being either the t-statistic or z-statistic.

The main difference between the t-statistic and the v-statistic lies in their applications and the conditions for which they are used.

The z-statistic:-

• Is used when the sample size is large (usually greater than 30) or the population standard deviation is known.
• The distribution of the sample data is approximately normal (z distribution is another term for normal distribution).
• The standard normal distribution has a mean of 0 and a standard deviation of 1.
• Is often used in hypothesis tests involving population proportions

The t-statistic:-

• Is often used when the population size is small )less than 30) and or the population standard deviation is unknown.
• The distribution is approximately normal, being especially important for small samples.
• The t distribution is similar to the standard normal distribution, but has thicker tails. The shape of the t distribution depends on…